I ran across a site that listed real X-Rated movies which have similar names to "non-X" rated films. To name a few:

As Good As Head Gets
Beaver and Buttface
Chitty Chitty Gang Bang
Desperately Spanking Susan
Honey, I Blew Everyone Again
On Golden Blonde
When Harry Ate Sally

Then I saw a *true* news story about famed porn star Ron Jeremy who is re-releasing his own all-time classic movie and an alien from outer space who has more than the standard two testicles. The alien tries to hook up with some Earth babes. It's called (I'm not making this up):

E 3: The Extra Testicle.

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Now, the actual joke.
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One day a construction worker left the job a little early, and when he got home he found his wife in bed with another man. Purple with rage, he hauled the man down the stairs and into the garage where he proceeded to secure his dick in a vice.

Utterly terrified, the man screamed, "Stop, stop! You're not going to cut it off, are you? ARE YOU?"

"Nope," replied the construction worker, "You are... I'm going to set the garage on fire."