Game Ufouria : The Saga

Ufouria is a (side scrolling) platform adventure video game. You begin play as Hebereke (Bop Louie in PAL regions), a penguin (though in PAL release he is more humanoid and looks like the Stay-Puft Marshmallow Man), and must explore the world on which you and three other friends crash landed. As you encounter the new characters you must fight them to make them recover their memory. Once you have recovered all 3 other characters you are then searching for Temple Keys which will lead back to your homeworld of Ufouria.

The world in which you interact is free form, meaning that you can wander around as you please. To get to new areas you will need to get power-ups and/or new characters with their own abilities. Character switching is done as needed, not defined by levels. Sections of the game have bosses and mini-bosses which include the characters which have not had their memory returned yet.