Season 6, Episode 4 - Super Mega Dance Show
The girls infiltrate an...evil dance competition?
While Alex enters as a contestant, Sam and Clover use the shrink-ray from the Versailles episode to sneak around (poof shrink).
They're captured by the villain (brief handheld) and stuffed inside dance shoes while the villain uses a machine to swap his leg with Alex's to win the competition...no, I'm not joking.
http://youtu.be/R3H5oa5ClgU?t=13m27s