Charlie tells Alan that Andy (Emilio Estevez) is like the brother he never had. In fact, Charlie Sheen (birth name Carlos Estevez) and Emilio Estevez are real-life brothers.
Emilio Estevez's character is named Andy, the same name as his character in The Breakfast Club (1985).
Alan says Charlie never made a will and Charlie seems surprised Alan got the house. But back in season 4, Charlie tells Alan that he and Jake are in the will to inherit the house.
Charlie mentions the heart of darkness when describing one of his hospital tests. Hearts of Darkness: A Filmmaker's Apocalypse (1991) is the name of a documentary about the making of Apocalypse Now (1979) which starred Martin Sheen, the father of Emilio Estevez and Charlie Sheen.