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!
Is it Giftpia?
Poptropica was never released for the Game Cube, it was released after the Wii came out.
Might it be Homeland? That game has an Animal Crossing-like graphic style, but I have no idea if it has anything to do with a jail.
It's Giftpia indeed. The game begins with you being sent in jail because you slept all day missing your adulthood ceremony, so you have to take multiple jobs to get money in order to redo the ceremony, otherwise you'll be forever a child.
Number one fan of characters that appear only once and ultimately were a recurring character either in disguise or trying a new image.
It was Japan-only, involved a tropical island, you start the plot having been put in and taken out of jail. Oh, it wasn't a Mario game at all, and at some point Wikipedia claimed that the currency in the game was Bells but doesn't anymore, and it wasn't an Animal Crossing game either, but had a similar POV.
I actually played it on an emulator back in the mid-2000s, which was impossibly slow for obvious technical reasons, so it did exist and I know it was not from a well-known franchise. The name "Poptropica" comes to mind, but the page for that lists a game for smartphones made more recently. Unfortunately Google can't find a trace of it, and searching "poptropica gamecube" just brings up a DS game related to the smartphone game.
Edited by SimYouLater