Yin Yang Carl: Carl discovers that Yin and Yang have forgotten Master Yo's birthday. So Carl tricks them into accepting a dangerous gift to give to Master Yo, so Yin and Yang won't be thought of as being thoughtless. But the gift is really a candle that once lit and blown out, switches the brains of Master Yo and Carl. Now Master Yo is in Carl's body, and Carl is in Master Yo's body. Carl plans to order the Woo Foo Warriors to their doom, while Master Yo finds out just what Carl has to deal with at his home. Antagonist: Carl (and Herman, to a lesser extent) Smorks: Master Yo has to go to a responsible parenting meeting and leave Yin and Yang at the dojo. He warns Yin to not take in any pets. But when Yin sees a bunch of seemingly harmless green creatures called the Smorks, she decides to take them in and protect them from Yang. But Yang thinks that the Smorks are harboring a dark secret and actually aren't that innocent. Antagonist: The Smorks