Or Driving Miss Daisy Chain?
My favorite was:
In Diana Jones and the Temple of Poon
Pornografied.
A lame knockoff of the magisterial Titty Titty Gang Bang, if you ask me. 
TV Tropes calls them Parallel Porn Titles.
And older than that to boot.
Up the Down Poopchute?
I’ve always wanted to film Sex Trek: Spock’s Cock, which would open on the bridge of the USS Extacy and lead to The Planet of Incredibly Horny Retarded Women:
“Cock and cock, what is cock?!?”
These are not (or mostly are not) puns. A pun is a type of joke that depends on a confusion between two possible meanings of the same (or very nearly the same) word (or homophonic pairs of words). The humor depends on their being at least a momentary confusion as to which meaning of the word is intended. That really is not happening with these sorts of porn titles. Words that sound a bit similar to ones in the original, non-porn title may be used, but they are rarely the same words, or homophones, and the difference is usually immediately clear.
The porn titles are pastiches of the originals, based upon wordplay that usually falls short of true punning. One might also call them parodies, especially if some sort of criticism of the original is implied (perhaps for being too staid, or unrealistically avoiding all reference to sex), but that rarely seems to be the case.
Pornocchio (a film from late 1970’s or so). Woodcarver sculpts a dummy, which seems to have nothing whatsoever to do with the rest of the film. Then he finds that he can only get a hard-on when he tells lies like “I’m from the government and I’m here to help you.”
Seems I also saw a blurb for a similar film, no cite, title “Penocchio” The tagline was “It’s not his nose that grows!”
I’ve always been amused by Beverly Hills Copulator.
The title, anyway. Never saw the film.
Porn parody history flicks are the best. “The Spanish-American Whore” and “Johnny Ampleseed” are shining examples of the genre.
I think Rule 34 is also relevant.
One of my personal fave titles has always been Yank My Doodle it’s a Dandy
I assume finding a dirty word that’s similar to the original title?
Harry Pooter & The Sorcerer’s Bone is my personal all time favorite.
As long as we’re naming favorites, I’ll add Spread Legged Freaks