The Grinch wakes up in a good mood one morning until his reflection in the mirror prompts him to repeat the "Grinch's Oath" and prove himself a Grinch. Meanwhile, the Cat in the Hat goes on a picnic. Their paths cross when the Grinch can't get his car around the Cat's, and things quickly escalate into a fierce car chase after the Cat unintentionally insults the Grinch by calling him "Mr. Greenface."