As in the original Shape Shifter, a mouse, a rabbit, and an elephant have all been bewitched into sharing the same body, and you'll need to swap between all of them in order to use their special skills to get through levels.
Use the [arrow] or [WASD] keys to move and jump, and the [1], [2], and [3] keys to swap between forms. Each critter has unique abilities to help them deal with obstacles, like the rabbit's extra-high jump and the elephant's... ability to wear mitts and handle hot objects, as elephants do.