In this episode, Dan's mother (Audrey) is played by Debbie Reynolds but was previously played by Ann Wedgeworth in an earlier Thanksgiving episode in 1989. A far more glaring plot hole is that it is mentioned in this episode that Dan was responsible for committing his mother to a mental hospital 20 years earlier which defies the character's complete normalcy and her Thanksgiving appearance less than 10 years earlier.
DJ explains to his grandmother that Return of the Jedi is a 1970's genre pic, like Empire Strikes Back. But both of these movies came out in the 1980s - Jedi in 1983 and Empire Strikes Back in 1980.