Grovyle appears in Pokémon Mystery Dungeon: Explorers of Time & Explorers of Darkness. Grovyle is a non-playable character (but he can be played in the Special Episode mentioned) in Pokemon Mystery Dungeon 2 and 3, with the exception of Special Episode #5: In the Future of Darkness, where he stars as the main character. He first appears in the main storyline as a thief who steals the Time Gears, however it is later revealed that he was doing so in order to take them to Temporal Tower and prevent the planet's paralysis. He is also the player's best and closest friend (Althought they don't remember due to amnesia) and therefore worried about the player and proved to be very protective of the player by taking a hit from Dusknoir that was meant for the player.
He is among one of the most important characters in the game.
At first, Grovyle is believed to be a villain, supposedly trying to steal the Time Gears to cause the planet's paralysis. He steals the first from Treeshroud Forest without resistance. The Time Gear of Fogbound Lake is stolen next after defeating Uxie and the fake Groudon. After that, he steals the Time Gear guarded by Mesprit, who was weakened by attacking the player and its partner. Finally, he defeats Azelf, intending to steal his Time Gear, but Azelf covers the lake in crystal to prevent him from getting it. The player's team confronts Grovyle, but despite their best efforts, they are defeated by him (while it is possible to defeat Grovyle in the battle, the cutscene is the same regardless). He nearly kills the player's partner, but Dusknoir, a famous explorer from the future who is trying to stop Grovyle as well, chases him off. Dusknoir finally captures him, but before taking Grovyle back to the future, he takes the player and partner with him. There, Dusknoir has his Sableye attempt to execute the player, their partner, and Grovyle. Thanks to Grovyle's quick thinking, they escape. The three find a Shiny Celebi, who Grovyle used to travel into the past in the first place, so the trio can return to the past. However, Dusknoir, his Sableye, and Dusknoir's master, Primal Dialga arrive to stop them. It is then that Grovyle learns that the player is in fact, the human partner he traveled back in time with.
Back in the past, Grovyle reveals that he and the player (as a human) were trying to solve the mystery of the paralyzed planet. After traveling to the past, the player and Grovyle got separated, with the player losing memory and turning into a Pokémon, and Grovyle attempting to find the Time Gears. Recovering the Time Gears was meant to stop Temporal Tower from collapsing, sending Dialga into a primal rage, and paralyzing the planet. Dusknoir, as opposed to stopping Grovyle from freezing time, had been sent back in time by Primal Dialga to ensure time would freeze. Grovyle, the player, and the partner recover the Time Gear of Treeshroud Forest, noticing that time had already stopped even with the Time Gear still in place. Grovyle heads out alone to recover the other Gears, made easier by the Team revealing the truth about him and Dusknoir to everyone else. They head to the Hidden Land, which leads to Temporal Tower. However, they are confronted by Dusknoir. After finally defeating him and his Sableye, Dusknoir reveals to the player that if the mission is successful, all Pokémon from the future will be erased from history. Grovyle confirms this and intercepts an attack by Dusknoir meant for the player. He is then forced to send himself and Dusknoir back to the future, leaving the Time Gears with the player and partner. After time has been restored, he, as well as Dusknoir, the player, and Primal Dialga, become erased from time. However, in return for their bravery and for the heartbroken partner, the player is restored by Dialga's time warping powers.
In Pokémon Mystery Dungeon: Explorers of Sky, the Special Episode In the Future of Darkness shows that Dusknoir, Grovyle, Primal Dialga, and the Sableye survive, but are trapped in the dark future. Primal Dialga orders for Dusknoir to be executed for his failure by Primal Dialga's army, but gets away with the help of Grovyle. The two of them team up together to defeat Primal Dialga. In the end, he, Dusknoir, and Celebi are spared by a being even higher than Dialga, allowing them to live in the future.
Grovyle is a powerful and skilled warrior. He's also willing to do anything to alter the dark future in which he lived, even if it meant dying himself or outright killing others, as he nearly killed Azelf and the partner when they stood between him and a Time Gear.