This Jigglypuff is a Normal/Fairy-type Pokémon that made its debut in The Song Of Jigglypuff. It continued to make an appearance throughout Ash Ketchum's journey up to Hoenn. After that, it returned to Kanto before ending up in Alola.
Jigglypuff are usually famous for their sweet voice, but this particular Jigglypuff has a problem with its voice, so Ash and Co. helped it to regain its voice, but Misty didn't catch it so whenever it arrives or whenever it comes on before a stage, it tends to sing, causing everyone who hears it to fall asleep. It seems to be unaware of its singing capability, and becomes annoyed when its audience falls asleep. When this happens, it uses its marker to draw markings on the faces both people and Pokémon alike as punishment.
First appearing in the The Song of Jigglypuff, Misty attempts to capture it, but Brock notices that this Jigglypuff has a throat issue. The group later helps Jigglypuff regain its singing capabilities, and upon singing to the group, becomes annoyed when they fall asleep. It rummaged through Ash's bag and found a marker, which it used to draw markings on their faces. Jigglypuff would later keep this marker to use as a "microphone" of sorts when it sings.
Jigglypuff later sang for the whole town of Neon Town, but because everyone feel asleep upon hearing it sing, it became annoyed and drew markings on everyone who attended. Despite being annoyed, Jigglypuff drastically changed the whole town, as everyone became significantly nicer to each other after the concert. It disappeared, but was shown to be following Ash and his group all the way to Hoenn.
It is believed that it started on a journey to find the one whom listens to it. This journey is believed to have ended when the gang encountered it one last time in Hoenn, where it found a Whismur that listened to the song all the way through, though its friendship with Whismur had ended rather abruptly.
Sun & Moon
This Jigglypuff later makes a reappearance in Alola, Kanto!, where it returned to Kanto. It emerges from the destroyed Meowth robot, where it proceeds to sing to group, causing everyone to fall asleep. As punishment, it drew markings on their faces. In When Regions Collide!, Jigglypuff is shown to be on the plane carrying the group back to Alola.
On the next few days after the birth of a Cosmog nicknamed Nebby during Pokémon School class in Now You See Them, Now You Don't!, Jigglypuff is shown to be singing at an Alolan karaoke when Nebby teleports Sophocles temporarily before return to the school, then both Ash and Pikachu at worst part alongside Nebby fell into Jigglypuff’s sleeping song, ended being doodled on their faces before they and Nebby teleports to another locations.
Jigglypuff later had a singing contest against Samson's Komala, and lost. It had its faced doodled on by Komala, and was delighted by it. It later petted Komala before floating away. Before it float to the Pokémon School where it meet its match Komala, it passed by singing in front of Team Rocket who are grabbed by Bewear at Melemele Island’s forest, with Jigglypuff’s doodle on Bewear’s face is by far scarier compare to its face doodle victims.
Many days after the recovery of Necrozma back to its heroic Ultra form in SM096, Team Rocket’s Jessie, who is currently infiltrating back to Aether Foundation’s shelter Aether Paradise while listing the guarded pack of Jigglypuff is glad that one of these said pack of Pokemon is not the same one she and Team Rocket knew, and Jigglypuff is revealed to be singing in front Grandpa Forest, who also fell into its victim by its sleeping song and face doodling.
It reappeared in the Pikachu short airing along with the 15th Pokémon movie.