By that definition, the return of classic Pokémon characters Brock and Misty (Takeshi and Kasumi in the Japanese version) in recent episodes of currently airing anime Pokémon Sun and Moon definitely applies.
So when the anime finally did start, Brock and Misty looked a little different from when they did in the games.
Brock and Misty were the original traveling companions of protagonist Ash (Satoshi) on his journey to become a Pokémon Master, but had been absent from the Pokémon anime for roughly 200 episodes.
Pokémon Red and Green, the paired Game Boy titles that kicked off the video game series, preceded the Pokémon anime by over a year.