Eighteen and Horny opens with balding, snaggle-toothed Dad putting the blocks to his wife while musing about his girl, Betsy. Although the wife has the breasts of a nineteen year old, Dad can’t help into Betsy’s room where, fortunately for him, Betsy relax with her mouth open… The next day, a rift erupts at Betsy’s birthday breakfast, and she packs her bags and runs away to the big city. There, she meets Chelsea, who offers her a place to stay. The crash pad turns out to be a gym where a wrestling instructor shows them some holds never seen on WCW. After a week of in-depth instruction, the girls are off to put on a private grappling exhibition for a fat cat who winds up pinning Betsy. Following an interlude of locker-room lesbianism, Betsy returns home where Dad tells her that Mom has had a nervous breakdown and is in the funny farm. Betsy reveals that she was awake when Pop porked her previously, and she shows him how much she liked it. But, in a shocking surprise ending…
