Martin's question to his mother, "You know the old Benjamin Franklin saying about houseguests and fish?" refers to the old adage attributed to the American Founding Father that, "Guests, like fish, begin to smell after three days."
Christine Ebersole plays Paul Reiser's mom with the help of aged-makeup; she's only three years older than Reiser, and she is younger than Michael Douglas, but is playing a character older than both.
At one point they are all watching the movie 'The Diner', Martin points out how he can barely see it. Martin is played by Paul Reiser who was one of the stars of the Diner. "Diner" was directed by Barry Levinson.