Held Captive

Listen up, genius! The joke is funny because it is unexpected that Carl Wheezer, the character known from Jimmy Neutron for his obsession with Croissants and his asthma, would hold someone captive. It's like, who would think that dude is capable of being a kidnapper? You know who else is not smart? You, that's who. You think putting pineapple on pizza is a good idea. Get outta here!