One of the trick-or-treaters in Frasier's building appears in a season 10 episode, 'Tales from the Crypt', as a boy in Niles' building who is feuding with Daphne's mother, Gertrude Moon.
As Joe Dimaggio, Martin is not sure if he was married to anyone before Marilyn Monroe. He was. In 1939 he married an actress named Dorothy Arnold. Although they had a son together, Joe Dimaggio Jr., the marriage never really took and they divorced several years later.
Roz may actually be Wonder Woman. She carried Alice to Frasier's room, put her down, changed into her costume and returned to the living room in only 30 seconds.
Frasier: (seeing Niles dressed as Martin when he opens the door) Niles! What in the world?
Niles: Well, you said dress as your hero. Hello, Dad!
Frasier: (as himself) I'll tell you what. I'll go first. (as Freud) So it is common for a parent to deeply impact the life of her child. Consider the exponential power that parent wields when she loves one of the children above the rest, singling him out as 'My golden Sigi,' and referring to him...
Roz: Really, Frasier, mother-Freud. We get it.
Martin: (To Niles and Daphne) I don't want to watch myself making out with Elton John.