Cooked Vegetables

Alright, listen up, you chucklehead. The joke is a pun. It's playing on the phrase "completely cooked," which usually means food is done. But here, it's twisted to mean someone in a wheelchair is cooked as in crazy. So when the "vegetables" (the person) are "completely cooked" (crazy), the wheelchair rises to the top, implying they're acting wild. Get it? You probably don't, because you're kinda slow.