When you find yourself trying to remember a show (or any works) that's on the tip of your tongue but just out of reach, come here - the collective brain of the TVTropes community can probably help. Post all the details you can remember (examples help). If you're looking for a trope, head over to Trope Finder. Have general questions about tropes? Visit Ask The Tropers!
It wouldn't have been the Shantae series, would it? It is a platformer that was on the GBA with a female protagonist, and I know one of the games has a sort of floating city...
Honestly, it actually has to be. I'm just dumb.
Non-licensed GBA platformer? Videogame
So back when I was a teenager and playing gba games on the computer through less than legitimate means and coming across a not great platform game. I feel fairly certain it wasn't a movie or tv show tie-in, I think it had a fairly distinctive english title and it definitely featured a female protagonist. I also recall there being a level called Skyport or something similar, but memories are a bit hazy. So probably an original IP, could have been part of a series. EDIT: I also remember there being a very annoying Mammoth boss
Edited by FirstSnow