Not sure how this one passed me by - only heard about it today - but it looks a lot of fun.
Basically, porn-star Ron Jeremy's dick gets detached from his body and is possessed by a sex-starved alien life-form. No, really. The penis-creature ("Juan" !!!???) then goes on a murderous rampage, attacking the cast and crew of an adult movie, who try and trap it - Scooby-Doo Style - "when it is limp and at its weakest." Their plan involves 'circumcising' it with an axe.
Well, you would, wouldn't you?
"If you see it coming - you're already dead."