The line "Good God, Lemon" is a clear reference to 30 Rock (2006), in which Alec Baldwin's character, Jack, uses this as a catchphrase. Also the movie upon which the title is based, Grumpy Old Men (1993), starred Jack Lemmon.
At a fan convention, Rose McIver said that the character of the brains Liv eats in this episode was her least favourite character in the series to play.
At 20 minutes in, Liv (Rose McIver) pulls a Walter Sobchak/The Big Lebowski (1998) quote: "a bunch of good men didn't die face down in the muck so you could...."
The episode title makes a reference to the Jack Lemmon and Walter Matthau movie, Grumpy Old Men (1993).