When Jack tells Janet about his dream six years ago when he moved in with the girls about owning his own restaurant, he was off by a year; it was actually five years and not six, since the show was aired in Spring 1977.
If you look closely at the magazine Janet (Joyce DeWitt) is reading, Viewpoint, the cover girl is none other than Priscilla Barnes.
When Jack trips the alarm and security approaches him you hear the cat's meow sound.