When they are excited, their legs become thrushed with crabs, and they get so excited about their own inadvertentness that at the end of the poem, they leak them as crabs and make fun of them.
"It's such a rude crab... I'm not going to let you go.' He’s a kid who gets pissed into his classmates’ desk while exposing himself in the classroom, an eccentric boy who shows his crotch face in the mirror and is out of jail, and a child who exposes a deceptive figure by live chat and leaks excited. Please see the sexual jealousy of a perverted woman who is excited about her own melancholy figure!