"A Case of the Evils" is the second segment of the twenty-first episode of Yin Yang Yo! It premiered on February 9, 2007 alongside "Attack of the Lesson".
Master Yo accidentally swallows some of Carl's backwash after accidentally drinking after him. This causes Yo to slowly become evil. Yin and Yang rush to try to save their master from the fate that has befallen him.
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