I wouldn't say the prank is wholly unfunny but it is sort of weak. It's based on a false scare of a somewhat reasonable basis.
The real hook on a good prank is to get someone to believe or perform something unreasonable.
Weak prank: Unbuttoning your blouse, mussing your hair and arriving at a friends house panting. When they let you inside you tell them that a pair of large men attempted to rape you and they're chasing you with a knife.
This prank reflects a real life fear and a scenario repeated a few dozen times every year around the country. It is within reasonable expectations and getting your mark to buy it is a dickish and lame thing to do.
Strong prank: Unbuttoning your blouse, mussing your hair and arriving at a friends house panting. When they let you inside you tell them that a werewolf attacked you and you barely got away. After you tell your story have a buddy with a werewolf mask pound on their window and make your friend freak the fuck out.
This is much funnier because not only did you scare your friend you got them to believe an unreasonable story about werewolves. You can then further humiliate them about their inability to tell fact from fantasy.
Steve Austin over here encapsulates a major aspect of religion rather nicely: subverting the rational part of peoples minds with fear then using that fear to control their reaction. Steve used the fear of amusement park ride accidents to get people praying by holding up some bolts. Many years before that someone else used the fear of hell to get Steve praying by holding up a Bible. They're both the basis of a lie used to influence people.
Using the werewolf vs. rapist analogy getting someone to believe in the Bible is funnier than getting someone to believe in a ride malfunction but at this point the joke has gotten stale and the effort people have put into it over the centuries has made the whole gag seem a bit overblown.