Quick: how do porcupines mate? If you answer: "carefully," you’d only be half right - it’s also "bizarrely." Indeed, porcupines have a very bizarre mating habit:

First of all, female porcupines are interested in sex only about 8 to 12 hours in a year!  Second, to court a female during the short mating season, a male porcupine stands up on his hind legs, waddles up to her, and then sprays her with a huge stream of urine from as far as 6 feet away, and drench his would-be paramour from head to foot!

If the female wasn’t impressed, she’ll scream and shake off the urine.  But, if she is ready, then she’ll rear up to expose her quill-less underbelly and let the male mount her from the behind (that’s the only safe position for porcupines!). Once mating begins, the female is insatiable: she forces the male to mate many times until he is thoroughly exhausted. If he gets tired too quickly, she will leave him for another male! (Source)