Fish Sticks South Park South Park- Do You Like Fish Sticks? I Don't Get This Joke!?

South Park- Do You Like Fish Sticks? I don't get this joke!? - fish sticks south park

A: Fishsticks?
B: Yes.
A: Fishsticks put in your mouth?
B: Yes.
A: What, you're a fish gay?

This is the last episode, but I do not understand it.