Continuity mistake: Timmy agrees to marry Russell because Timmy's work visa has expired and he will have to leave the country. However, in the season 5 episode "Double Down" Timmy states that he has been a US citizen for many years.
Rules of Engagement (2007)
Episode list - season 4
Starring: Patrick Warburton, Bianca Kajlich, Megyn Price, Oliver Hudson
More mistakes in Rules of Engagement
Jeff Bingham: Don't play dumb with me. It's a game you can't win.