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 was really a candle that once lit and blown out, switches the brain's of Master Yo and Carl! Now Master Yo is in Carl's body, and Master Yo is in Carl's body! And 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. Will anybody survive this ordeal?