Banana slugs checking each other out for size (Image Credit: Husond, Wikipedia)

Banana slug, the beloved mascot of UC Santa Cruz, has a weird mating habit. First of all, they have an enormous penis. (In fact, their latin name dolichyphallus translates to "giant penis.") The average size of a banana slug penis is 6 to 8 inches. This is incredibly impressive, considering their entire body length is 6 to 8 inches as well!

Banana slugs are hermaphrodites, so two slugs will try to fertilize each other. To mate properly, a slug must choose a mate roughly its own size - if it miscalculates, its penis will get stuck during copulation.

This isn’t just an embarrassing faux pas, the other slug will actually bite off the stuck penis, a term scientists euphemistically called "apophallation." (Source)