Fruit and Vegetable

Alright listen up, you dum-dum. The joke is makin' fun of a gay dude in a wheelchair. "Fruit" is slang for a gay person, and "vegetable" is a rude way of sayin' someone is messed up in the head or can't move. So, this John guy is bein' a jerk by sayin' the dude is both gay (a "fruit") and disabled (a "vegetable"). It's not cool, and people like you probably think it's funny 'cause you're not exactly rocket scientists yourselves.