He doesn't even seem human most of the time. He's just a walking joke with no punchline. The premise of this movie is that the world was blown up in a nuclear war ten years ago. Now the human race has been almost wiped out, and frogs have mutated into intelligent, bipedal, evil creatures. Most of the human race has been sterilized by the radiation, and women outnumber men.
Fertile women are a rare commodity, but fertile men are even rarer.
Enter Roddy Piper. He's a criminal drifter who has apparently left a string of pregnancies behind him wherever he's been. He's taken to the labs of Medtech after being captured by an evil border guard, and they press him into service. It's an easy decision. It seems that the evil frog people have raided a border town and stolen a bunch of fertile women.