In this episode it is revealed (at least, according to a rag) that Moe's father is a Yeti.
When The Mayor turns on the jukebox, everyone starts partying. Lou comes in and dances with them and you can see Lionel Richie in the background. He was from the episode where Homer flew on a private plane. It's also an homage to the video for 'All Night Long'.
When sideshow Bob enters the bar in the "Cheers" part of the couch gag opening it is a nod to him being voiced by Kelsey Grammer. Kelsey Grammer is most well known as the character Fraiser Crane, who started out on "Cheers"