Deliberate mistake: In the scene where Alicia Silverstone and Dave Foley are in the porno store, they cut to a guy standing behind a counter. All of the explicit shots of the videotape covers on the countertop are blurred out.
Factual error: After some tinkering with a TV set and a mirror, Calvin Webber finds that he can watch a TV show in reverse image. On the screen is the opening of "The Honeymooners" showing the cast members' names superimposed on a picture of the moon, with Jackie Gleason's face. But the picture is in color, mostly blue and off-white, while the actual "Honeymooners" series was filmed in black-and-white.
Chosen answer: I think this is a reference to two things: home shopping networks (which often offer free inducements such as lawn furniture or steak knives to shoppers who "call now" or "act now"; it's also probably a reference to Calvin's age - elderly people liking lawn furniture.
Sierra1