Trivia: When the Tri-lambs are watching the Pis on television, Pointdexter ejaculates in his pants which causes a fit of laughter. The laughter is coming from director Jeff Kanew.
Trivia: When director Jeff Kanew was interviewed by the producers, they asked what kind of movie he thought he could make given the material. He responded, "One I would be embarrassed to have my name on." They hired him immediately.
Trivia: The University of Arizona agreed to let the filmmakers shoot at the campus but then revoked permission after reading the script and discovering how raunchy it was. Eventually they again changed their minds and let them shoot. They also allowed many of the students to be used as extras.
Trivia: At the time the movie came out, the term "Alpha Beta" for the jocks was funny to moviegoers because Alpha Beta was a well known supermarket chain at the time. It went out of business around late 80s/early 90s so nowadays the meaning behind the joke is somewhat lost.
Answer: First, Lewis and Betty are not "having sex" - he is raping her, and the writer and director later described it as "not excusable" (https://decider.com/2019/07/26/revenge-of-the-nerds-rape-scene-regret/). Second, the song you hear is "Right Time for Love" by Jill Michaels and Pat Robinson. It was not written for the film.