I always wondered why she didn't get Poliwag back in Kanto. Kanto oddly enough has no filler for the Poliwag line at all. They should have her Misty get it back then, use it as her main battler, etc. Instead she really only had Staryu that couldn't develop because it had no personality and couldn't evolve either because she already had a Starmie. Poliwag was the closest thing Misty had to a pokemon that developed naturally over the course of her run, even if Politoed didn't do much by the end of Johto but cheer.