Bulbasaur is frequently viewed as the responsible leader of Ash's Pokémon, especially due to his actions at Professor Oak's lab. It is also a Pokémon Ash values more than most of his other Pokémon, possibly because he always wanted to catch one, as explained in Bulbasaur and the Hidden Village, although it was his second choice as a starter, after Squirtle. It also formed a bond with Pikachu and Squirtle while they fought together while part of Ash's team. But, at the start, he disliked trainers as shown in Island of the Giant Pokémon where it said, "Maybe Ash has forgotten about us".
In Make Room for Gloom, Bulbasaur is shown to be attracted to Florinda's Gloom after giving the antidote from its head to cure its paralysis after it smelled the Stun Stem and blushes when it comes to Gloom as the latter did the same when they are together. Bulbasaur was also defended by Gloom when everyone is paralyzed from Meowth's paralysis bomb and also shared Bulbasaur's Solar Beam which it was used to blast Team Rocket off into the sky. Bulbasaur soon shows his attraction while licking on Gloom's face after saving them. Both Bulbasaur and Gloom are now good friends as both try to get some fertilizers inside the greenhouse and gives it for Ash to delivered it for his mother, Delia.
Bulbasaur's best friend in the group is Squirtle, whose immature, fun-loving personality contrasts with Bulbasaur's serious, mature one. Nonetheless, all of Bulbasaur's immature acts have something to do with Squirtle, such as Bulbasaur angrily chases Squirtle after it accidentally ate the Bulbasaur-shaped cookie that it likes to eat, or using Squirtle as a sled after witnessing Pikachu, Togepi and the junior Kangaskhan enjoying themselves on actual sleds which are later followed by Geodude, Vulpix and Psyduck who are hanging on Onix who serves as a large sled.
Both Bulbasaur and Squirtle are always seen teaming up together when they compete against Snubbull and his group during summer vacation and throwing snowballs on Pikachu during winter vacation. When Squirtle was leaving, Bulbasaur looked away while shaking its hands/vines, sad to see its friend go. However, they briefly reunited together during the Silver Conference and both also gain a bitter rivalry towards Jackson's Meganium and Azumarill, who makes fun at both of them.
In Gathering the Gang of Four!, Bulbasaur reunites with Pikachu upon reunion as they briefly play together. But when its best friend Squirtle arrived to see them both, they are seen having a friendly hug as part of their reunion.
In Hokey Poké Balls, Bulbasaur also became friends with May's Bulbasaur when they briefly play together and he teaches her how to handle against James' Cacnea and Jessie's Seviper after she was unable to negate their attacks and later they work together to knock them down with their Vine Whip as the two are later seen doing a Vine Whip high five. Bulbasaur finally stays with May's in the later episode The Right Place and the Right Mime so that May allows her Bulbasaur to stay at Oak's lab to learn more from Ash's until she evolves twice in her evolutionary stage.
During Alolan's Pokémon School Anniversary trip in Kanto when Team Rocket attempt to capture Bulbasaur, Pikachu and the rest of Alolan trainers' Pokémon, Bulbasaur was temporarily afraid of Jessie's Mimikyu for its murderous aura, which is meant to kill only Pikachu, until Bewear's sudden arrival to take Team Rocket back to Alola.
Ash's Bulbasaur resides at Professor Oak's Pokémon Lab, and constantly acts as a peacemaker and an ambassador between the rest of the Pokémon who were Grass-type and Water-type.
Bulbasaur was raised in the Hidden Village by Melanie, who cared for sick, injured, and abandoned Pokémon. Bulbasaur acted as the village's bodyguard, but after Ash helped defend the Hidden Village from an attack by Team Rocket, Melanie encouraged it to join Ash, explaining that its growth was being stunted by staying too long in the village. Although Bulbasaur initially appeared to distrust Ash, it agreed to join him. It alone assumed that Ash had abandoned it and the others when they were separated from him following an attack by Gyarados after escaping the sunken St. Anne cruise ship. Its views on Trainers were presumably colored by all the abandoned Pokémon in the Hidden Village. Over time Bulbasaur grew to trust its new Trainer.
Bulbasaur is extremely stubborn, surly and eager to battle. Although its surliness has lessened. It battled against Erika's Tangela and lost during Ash's Gym Battle in Celadon City, but redeemed itself when battling against Aya's Venonat, where it sent Stun Spore back at it by blowing at it and beat it with Leech Seed.
It had the opportunity to evolve after battling a powerful Rhyhorn belonging to a Hiker Trainer with a very strong Take Down attack. However, Bulbasaur overhears Ash's excitement of his Bulbasaur evolving into an Ivysaur while he was talking to Nurse Joy about its condition and the evolutionary festival. It soon becomes worried about its condition as Pikachu comforts it. Therefore, Bulbasaur was captured by several Bulbasaur who take it through the mysterious garden where the Bulbasaur held the evolutionary festival as Bulbasaur tells Pikachu to warn Ash about its situation.During the evolutionary festival at the mysterious garden headed by a Venusaur, the mass of Bulbasaur glow their bulbs due to its control of nature and evolve to Ivysaur. But Ash's Bulbasaur refuses to evolve, much to Ash, Misty, and Brock's surprise as Ash defends it from Venusaur's Vine Whip when Bulbasaur constantly refuses to evolve, angering the Venusaur. Ash apologizes to the Venusaur for ruining the evolutionary festival, especially to Bulbasaur after overhearing of his excitement to make him evolve and not knowing whether he likes it to evolve or not. Ash tells Venusaur that they can't force his Bulbasaur to evolve the way they wanted and it has a right to decide when it was ready to evolve. As Venusaur is considering whether to let Ash's Bulbasaur evolve on its own terms or not, Team Rocket intervenes and manage to capture the mass of Ivysaur with their sucking machine. Venusaur tries to save them with its vines but Team Rocket increases their machine to full power to make Venusaur find itself struggling to avoid being sucked in as well, especially Ash's Pikachu, which was saved by Bulbasaur using its vines. Bulbasaur does its best to save them by hitting the sucking machine with a Razor Leaf, but it didn't do a thing as James knew it was the only one left behind while both Jessie and Meowth maniacally laugh at it, causing Ash to get mad for making fun of it. Bulbasaur grew angrier even further at that insult and it yells to make the sun rise. This allowed it to learn the powerful Solar Beam much to Ash's surprise even through his Pokédex. Bulbasaur's bulb had glowed into a yellow light to unleash this ability to cut through the sucking machine, quickly leaving Team Rocket in stunned shock and horror, before it exploded, followed by its Razor Leaf to rescue the mass of Ivysaur inside the bag as the Meowth Balloon basket falls to the ground. The mass of Ivysaur, including its head Venusaur and Ash's Bulbasaur, angrily glares at them, much to their horror. The Team Rocket trio are eventually blasted off by Ash's Bulbasaur, Venusaur, and the mass of Ivysaur with their Vine Whip. Venusaur gains a great respect towards Bulbasaur after being saved along with the mass of Ivysaur and finally understands its decision and it happily shakes hands/vines, showing its respect for each other. Ash, Misty, and Brock give a happy farewell to Venusaur and the mass of Ivysaur in the mysterious garden and Bulbasaur happily watches them leave.
It has the heart of a fighter and it never gives up in a battle. It has the determination to keep fighting even if the odds are against it, defeating such varied opponents such as a herd of Exeggutor, despite the disadvantage. It also beat Jeanette Fisher's Beedrill with Tackle and went on to battle Scyther despite the type disadvantages. After some trouble, he used Vine Whip to hit every Double Team clone and then hit the real Scyther with both vines knocking it out. Ash tried for the sweep with Bulbasaur, but he fell to her surprisingly strong Bellsprout. On one occasion, Bulbasaur, along with Pikachu, was briefly lent to Misty to allow her to compete in the Princess Day Festival with a more balanced team, Bulbasaur single-handedly winning her first match by defeating a Kingler, Pinsir, Cubone, and Raticate on its own.
In Make Room For Gloom!, Bulbasaur was enjoying being inside the Xanadu Nursery as he also smells some plants that make him act oddly until he ends up paralyzed when it smelled the Stun Stem. Bulbasaur was carried by Florinda's Gloom while being helped by Ash after Florinda warns him about the Stun Stem.
Gloom uses the antidote for paralysis to cure Bulbasaur as its nectar drips into its mouth. Bulbasaur was thankful for Gloom curing its paralysis and became attracted to Gloom while blushing at it and the latter did the same and Misty thought they have a budding romance. When Team Rocket attempts to steal the plants, Bulbasaur confronts them with the others, but they were paralyzed by Meowth's paralysis smoke bomb. Gloom defends them as Florinda was convinced by Brock to fight Team Rocket and showing her confidence by telling Gloom to use Double Team and blasts them off with its Solar Beam. Bulbasaur licks Gloom's cheek after saving them, which Gloom blushes for it. After the incident, both Bulbasaur and Gloom became best friends and both are seen going inside to get the fertilizers for Ash to deliver to his mother, Delia, who requested him to get some.
Bulbasaur was also used to battle against Drake, the Orange League Champion, and his Electabuzz. Bulbasaur is not damaged by Thunder Shock and hits it with Razor Leaf. Bulbasaur then lands a Tackle but is knocked out by Thunder Punch.
Bulbasaur was used to capture Heracross, who started sucking sap from its bulb, much to his annoyance. Bulbasaur became the only member of Ash's original team, save for Pikachu, to remain in his care, while it watched its best friend Squirtle and companion Charizard leave.
It battled against a wild Chikorita that Ash wished to capture. It also released by Ash among with other of his Pokémon and immediately shoves Heracross away using Vine Whip when it attempts to suck its bulb. It later teams up with its best friend, Squirtle and Zackie's Bellsprout to rescue Pikachu and to get their remote as well as thwarting their plans to steal the Sprout Tower itself from their rocket.  It was also used to fight Team Rocket but was annoyed by Heracross, who was sucking the sap from his bulb. It was also used to battle Misty to decide who gets to keep Totodile. Bulbasaur looked set to beat her Poliwag with Razor Leaf, but it evolved into Poliwhirl and hit it with Bubble. Bulbasaur then flattened Poliwhirl with Solar Beam, winning the match for Ash. It also had a rematch with Aya and crippled it with Leech Seed once more, but this time, Venonat came back and almost won with Supersonic and Tackle, but Bulbasaur knocks it out with by throwing it with Vine Whip.
Bulbasaur had stayed with Ash until midway in the Johto adventures in the episode, Bulbasaur... The Ambassador!, when it was sent back to Professor Oak's to keep the Pokémon there from quarreling with each other. When Bulbasaur was mauled with both grass and Water-type Pokémon while Ash's Heracross and Tracey's Marill, Venonat, and Scyther try to stop them from beating Bulbasaur up, the fight stops when Bulbasaur unleashes its Solar Beam as the two wild Bellossom do a peace dance. Bulbasaur serves as a peacemaker of both water and Grass-type Pokémon and seeing their quarrels because of the dispute of the Water-type Pokémon lake. It decides to make a new lake for Grass Pokémon by digging and it also convinces a wild Poliwhirl to wash the ground with Water Gun and three Sandslash to Dig. Once the lake is already made, it saved an Oddish from a falling boulder, as both water and grass Pokémon are saddened thinking it was killed and Bulbasaur was revealed to be alive by using Dig after remembering its travels with Ash in Kanto. Professor Oak convinces Ash to keep Bulbasaur at his lab to serve as its peacemaker, which Ash agrees. Bulbasaur is last seen watching stars knowing that he will miss Ash, Pikachu, and its friends.
Bulbasaur came back alongside its best friend Squirtle in the Johto League, where Squirtle was mocked by Jackson's Azumarill, who also slaps Bulbasaur in the face, which Squirtle becomes angry for what it did. Bulbasaur calmly restrains them, but the better half of the duo joins the fray when Jackson's Meganium mocks it by tripping its leg with its Vine Whip while laughing at both of them causing Bulbasaur to get angry as well. Both Bulbasaur and Squirtle had a bitter rivalry towards both Azumarill and Meganium as they fought them both in a cockfight only to be calmed down by Harrison's Miltank, who uses its Heal Bell to stop them from fighting.
He battles against Jackson's Magneton, who had defeated two of Ash's Pokémon in the 3-on-3 match. Bulbasaur learned from Pikachu and Cyndaquil's mistakes, and despite being the most disadvantaged one out of the three, he takes the win with Leech Seed and Vine Whip. He then battled against Meganium, whom he still had a bitter rivalry for the pride of Grass-type Pokémon. Despite Bulbasaur being tired from the previous battle while Meganium is healthy, Bulbasaur dodges Body Slam and lands a Razor Leaf, while being hit by Meganium's Razor Leaf. It reverses its Body Slam by using Vine Whip around its neck and pelts it with Razor Leaves and Vine Whips, before a double Solar Beam takes them both out, resulting in a tie for the two trainers, and Ash advancing to the next round.
Advanced Generation Series
Bulbasaur continues to reside at Professor Oak's lab along with Ash's Bayleaf, Cyndaquil, Totodile, Noctowl, and the rest of the Pokémon, where they discovered that both Golem and Nidoqueen are actually Butch and Cassidy in disguise to steal all the Trainer's Pokémon. Professor Oak chooses Bulbasaur to fight off Butch's Hitmontop, which it defeats it with Vine Whip while being assisted by Tracey's Scyther. After defeating their Pokémon, Bulbasaur hits them hard with Solar Beam until Totodile blasts them away with its Hydro Pump. Bulbasaur later continues to watch over all the Pokémon in Professor Oak's lab along with Ash's other Pokémon.
Bulbasaur does its best to stop all of the Tauros from getting stampede but failed and they bust in Professor Oak's lab but all of the little starter Pokémon ran away. Bulbasaur also does not impress the town mayor's son, Gilbert who likes to pick all of Professor Birch's starters in Hoenn rather than the ones from Kanto. After Tracey finds Charmander in the river stream, Bulbasaur was aided by Professor Oak and Gilbert and they saw Squirtle is about to fall off. Due to Gilbert's arrogance and wants to leave, he falls into the edge but was saved by Bulbasaur with its Vine Whip while Professor Oak catches the falling Squirtle in time. By the time to find a little Bulbasaur who is trying to avoid getting pummeled by several Primeape. Delia let Mimey use Psychic to keep Bulbasaur safe until it was disrupted by Gilbert who sneezes causing them to be chased by it. Both Gilbert and the little Bulbasaur ends up in a cliff, they are rescued by Ash's and puts them to safety and faces all of the Primeape. Bulbasaur scares them by shooting a Solar Beam much to Gilbert's amusement and it scares all the Primeape away in fear.
Because of Bulbasaur's bravery, Gilbert finally chooses the little Bulbasaur as its starter Pokémon and it watches Gilbert leave to start on his journey with the little Bulbasaur as his partner.
Bulbasaur later returned to meet May's Bulbasaur, after it manages to catch Bulbasaur's Poké Ball with its Vine Whip after they failed to catch Team Rocket and the two Bulbasaur quickly became friends. Both Ash and May's Bulbasaur teamed up to find the missing Poké Balls which are stolen by Team Rocket. When James activates the cabin into a large steel guard building, May, Max along with two Bulbasaur manage to get through the roof as their Vine Whip is used to get what's stolen. Pikachu manages to knock through the wall with Iron Tail. Cornered, Jessie and James use Seviper and Cacnea to attack May's Bulbasaur who is unable to negate their attacks even her Razor Leaf. After Ash's Bulbasaur intercepts Cacnea's Pin Missile attack with Vine Whip to defend May's, both of them use Vine Whip to send Seviper and Cacnea flying towards Team Rocket while Brock calls the two Bulbasaur as Team Bulbasaur which Team Rocket gets upset for mocking their group's name. They send their Pokémon to attack again, but Pikachu uses Thunderbolt to blast them off after Brock retrieves all of the Poké Balls they had stolen and the two Bulbasaur perform a high five with their vines. Afterwards, Nurse Joy and the kids are thankful to both Ash and May's Bulbasaur to retrieve their Pokémon Balls until Bulbasaur was transported again by Professor Oak due to Water and Grass-type Pokémon are fighting at his lab. Before being transported back to Professor Oak's lab, Bulbasaur bids farewell to May's Bulbasaur while it happily patted her head with its vines. They were used to battle Team Rocket's Pokémon before the former are attacked by Misty's Azurill and Tracey's Marill's Water Gun followed by May's Combusken Fire Spin and Pikachu's Thunderbolt to blast them off. May decides to leave her Bulbasaur with Professor Oak so she can learn from Ash's.
It returns again along with Charizard and Squirtle to battle Brandon at the Battle Pyramid in Gathering the Gang of Four!. Ash releases his Bulbasaur to make a reunion with his Pikachu as well as its best friend Squirtle as the trio are seen in a friendly hug until the arrival of Charizard. When Charizard is causing mischief towards its best friend Squirtle, Bulbasaur tries to discipline him with Vine Whip but Charizard dodges as it slaps Pikachu by it causing the latter to get mad even Ash tried to calm them down but failed as Pikachu electrocutes them with its Thunderbolt. As they a campfire at night, Ash reminisces his Bulbasaur way back when he guards the other Pokémon at the Hidden Village owned by Melanie and becomes the peacemaker between both Water and Grass-type Pokémon at Professor Oak's lab. Bulbasaur can be seen training with Ash along with Pikachu, Squirtle, and Charizard for the battle against Brandon.
When Pikachu was captured by Team Rocket, Ash along with Bulbasaur and Squirtle to be mounted on Charizard as it flies to pursue the Steel-type Meowth Balloon. Bulbasaur uses Razor Leaf but it didn't do a thing as both Charizard and Squirtle's attack won't work either. Ash becomes relentless to see this, as it uses a combination of both Charizard and Squirtle's Flamethrower and Water Gun combination to make a crack on the steel Meowth Balloon allowing Bulbasaur to destroy it using Razor Leaf to make them fall into the ground. Team Rocket is eventually blasted off by Pikachu's Thunderbolt, Squirtle's Water Gun, Bulbasaur's Razor Leaf and Charizard's Flamethrower. Brandon arrives to see Ash and his first four of his old Pokémon and became impressed to see them defeating Team Rocket. Ash was amazed to see him and his assistant had told him about he had found a new Pokémon which Brandon knows. Brandon suggests having a battle in a 4 on 4 to know more of four of Ash's Pokémon which Ash agrees to his deal. At the Battle Pyramid, it battled against Brandon's Dusclops after it manages to bring down Charizard. Bulbasaur was able to endure the unavoidable Shadow Punch and land a hit with Leech Seed but struggled to overcome the Confuse Ray/Mean Look combination. Ash snapped it out of the confusion and defeated it with Solar Beam. Solrock's Psychic attacks were tougher to overcome, but in the end, both Pokémon were knocked out with a double Solar Beam. Bulbasaur then returned to Pallet Town with Professor Oak after the battle.
Bulbasaur reappears at Professor Oak's Laboratory, where Heracross is sucking sap from its bulb, much to Bulbasaur's annoyance. It used Vine Whip to shove Heracross away.
Bulbasaur reappeared in a flashback when Ash was explaining the story about his Charizard. It reappeared again where it greeted both Ash and Pikachu while it was with Professor Oak being interviewed by Alexa. It was happy to see Pikachu again. As Ash requested, Bulbasaur happily releases its Solar Beam to get all of Ash's Unova Pokémon's attention in a shining multiple of sparkles. Unfezant, Krookodile, Leavanny, Boldore, and Palpitoad finally reunite with Oshawott, Snivy, Scraggy, Pignite, and Charizard after they were taken out by Ash.
Bulbasaur reappears during Ash's flashback where he retells to Misty and Brock about the Mysterious Garden headed by Venusaur which Ash defends it due to Bulbasaur who doesn't want to evolve like the others who were evolved into Ivysaur. It reappears again where it was seen breaking the fight between an Oddish, Gloom, and Vileplume and a Bellsprout, Weepinbell, and Victreebel and being reunited with Ash, Brock and his new Alolan friends, Kiawe and Sophocles. When Brock tries to calm down a wild Onix, it, Ash, Sophocles, and Kiawe are briefly relieved before Kiawe's Marowak attacks it causing the wild Onix to chase them as Ash carries Bulbasaur during the chase. Bulbasaur was captured along with the rest of their Pokémon by Team Rocket only to be released by Brock's Crobat, Misty's Staryu and Ash's Lycanroc who destroy the Meowth robot before Bewear drags them away in flight.
After Jigglypuff put them to sleep and has marks made by it, Bulbasaur was last seen eating with the others outside at Professor Oak's lab.
- Bulbasaur is the first starter Pokémon Ash ever captured.
- Bulbasaur was the first Grass-type Pokémon that Ash has owned.
- Bulbasaur is the second Pokémon Ash owns that chose not to evolve, the first being Pikachu, but he is the first Pokémon that Ash caught that chose not to evolve because Bulbasaur was not ready to evolve yet. Pikachu wants to prove that he can defeat stronger Pokémon without evolving.
- Bulbasaur is possibly the de facto leader of Ash's Pokémon that are at Prof. Oak's lab.
- Bulbasaur is one of Ash's original six Pokémon, now also counting Charizard (other than Pikachu since Pikachu is always with Ash) that he still has.
- Despite being part Poison-type, Bulbasaur does not know any Poison-type moves.
- Bulbasaur, after Pikachu, is the Pokémon Ash has owned for the longest time period. It is the only member of Ash's original team, besides Pikachu, to remain in his care, and the only one to reside at Oak's lab.
- Bulbasaur is also the second most returning character, with the first being to Charizard.
- ^ IL051: Bulbasaur's Mysterious Garden
- ^ IL010: Bulbasaur and the Hidden Village
- ^ IL017: Island of the Giant Pokémon!
- ^ IL026: Pokémon Scent-sation!
- ^ IL032: The Ninja Poké-Showdown
- ^ IL051: Bulbasaur's Mysterious Garden
- ^ IL043: The March of the Exeggutor Squad
- ^ IL079: The Fourth Round Rumble
- ^ IL052: Princess vs. Princess
- ^ OI032: Enter The Dragonite
- ^ JE003: A Sappy Ending
- ^ JE031: The Fire-ing Squad!
- ^ JE018: Charizard's Burning Ambitions
- ^ JE010: The Chikorita Rescue
- ^ JE014: A Bout With Sprout
- ^ JE020: Chikorita's Big Upset
- ^ JE035: The Totodile Duel
- ^ JE060: Ariados, Amigos
- ^ JE109: Bulbasaur... the Ambassador!
- ^ JE152: Tie One On!
- ^ Showdown at the Oak Corral
- ^ Journey to the Starting Line!
- ^ AG074: Hokey Poké Balls
- ^ AG134: The Right Place and the Right Mime
- ^ AG190: Gathering the Gang of Four!
- ^ AG191: Pace - The Final Frontier!
- ^ DP182: An Old Family Blend!
- ^ BW118: The Fires of a Red-Hot Reunion!
- ^ BW144: The Dream Continues!
- ^ SM042: Alola, Kanto!