Suzanne asks for a 5-letter Star Wars planet, as a clue in a crossword. They answer Endor, which is mistakenly thought of as an error. However, Endor is the name of the planet. What is typically referred to as "Endor" is actually the forest moon of Endor. Several characters in Return of the Jedi do say "Forest moon of Endor."
When Bill is pitching the idea for his movie, the 2nd time he takes a drink (right after the waitress brings new ones) you hear ice rattle as he brings the glass up and then back down, but there's no ice in the drink he has.
The movie takes place in 1998 just before Mark's 30th birthday party, putting his birthday in 1968. However, in the flashback scene of Mark trying to get into Star Trek: The Motion Picture Mark says his age is 12 when asked by the women in the ticket stand, despite the fact that Star Trek: The Motion Picture was released in 1979 and the movie itself says 19 years earlier. This would make Mark already 30 by the time the film is taking place in 1998.
Reflected in picture frame when Illa pulls Mark off the couch.