Pokémon: What happened to Mist's Pokemon?
Kasumi's Pokémon in the Pokémon anime is almost as much a fixture of the series as Pikachu, but what happened to her after Kogi left?

Anyone who has watched the previous seasons of the Pokémon anime will recognize Misty's Togepi, and she is almost always depicted as carrying it from the moment it hatches. But what happened to Togepi when Misty left the Pokémon anime, and why wasn't she featured in later appearances?
Misty's Pokémon hatched from an egg Satoshi found at their excavation site looking for Fossil Pokémon. It only kept the egg for a few episodes, and though the three friends held a contest to see who could keep it, when it hatched, Togepi imprinted Misty as its mother, solving the problem forever. Misty's Toxopi, like Pikachu, is always kept out of the Poke Ball and never fights, though it occasionally uses the metronome, especially to get rid of Team Rocket. When Pokémon's Misty and Ash parted ways before he set off for Hoenn, Togepi went with her.
Misty set a trend that many of Ash's future companions would follow, and she did make a cameo in the Ruby and Sapphire Pokémon anime. In one such appearance, in a two-episode episode titled "Princess and Pokemon/Pokepy Mirage!", Misty met Join Ash and his new travel companions for the "Togepi Festival" in a place called Mirage Kingdom. However, the festival is a trap for Team Rocket and the Togepi is stolen, so the team sets out to save it. Team Rocket isn't alone this time, however; instead, they stole Togpi on behalf of a man named Colonel Hansen, who wants to be the new ruler of the Phantom Kingdom. Tradition in the kingdom dictates that the new ruler must be chosen by the pure-hearted Pogpi, usually from a place known as the Pogpi Paradise. Togepi escapes but is found by the kingdom's rightful ruler, the young princess Sara. After Sarah found out that this Pokemon was Xiaoxia's Pokémon, they teamed up to stop Colonel Hansen. Misty's Togepi evolves into Togetic and stays behind to watch over Togepi Paradise. Pogby from Heaven chose Sarah to keep the kingdom safe under her rule. After a tearful goodbye, Xia, Zhi, and the others returned to Hoenn, and Xia parted ways with them again.
Togetic Follows in Many Other Pokémon's Footsteps

Togetic is not the first Pokémon belonging to the protagonist to be left behind like this. Ash unleashes his Pidgeot so it can protect a group of Wild Pidgey in much the same way. Squirtle and Lapras also left behind a pod of Pokémon, although in that case, they were once part of it. Since this episode is about 45 episodes after Misty's departure and isn't really mentioned again, though, it's easy to miss that and then wonder where Togepi was during Misty's other later Pokémon reappearances, such as in Sun and the moon. Since Pogby hasn't actually appeared yet, it's safe to assume that Pogby continues to watch over the heavens, happily caring for a young Pogby.
While it's a shame that the iconic aspects of the series didn't carry on, Misty moved on and featured various Pokémon in her later appearances. As the anime will wrap up its time with Ash by bringing back Brock and Misty, maybe Togetic will also make one last appearance.