The plot starts with Kim and Ron going to Monkey Fist's castle to get the Mystical Monkey Idol before Drakken and Shego can. The two duos end up fighting. However, the Idol's power causes Ron and Drakken to switch bodies. Professor Dementor swiftly proceeds to pop up and steal the Idol himself. It's up to both Kim and Shego to get the Idol back and switch them back.
What's the Switch? is the first, and only, Kim Possible title released on home consoles. Like its predecessors it's a sidescroller, however this game is fully 3D. Kim is playable in all levels, Shego is playable in all-but-one, and Rufus is playable in three levels. The game also has multiplayer modes.
This game provides examples of:
- And Your Reward Is Clothes: You can unlock various costumes for both Kim and Shego.
- Clothing Switch: Amongst the unlockables is Kim's outfit for Shego and Shego's for Kim.
- Enemy Mine: Kim and Shego team up to get Ron and Drakken back to normal.
- Evil Laugh: At the start of the game Professor Dementor runs out in his exit, returns directly afterwards because he doesn't think that's villainous, does an evil laugh, and then runs for real.
- "Freaky Friday" Flip: The main crux of the plot revolves around Ron and Drakken switching bodies, forcing Kim and Shego to team up to undo it.