Roz's Krantz & Gouldenstein are Dead - S4-E15
Continuity mistake: Frasier is on the couch talking to Niles. As he says "I simply release my humble words", his hand switches from being around the middle of his bottle of water to being around the neck, with no time for natural change.
Roz's Turn - S4-E17
Continuity mistake: When Frasier, Roz and Bebe are arguing, Frasier says something like "she has no reflection." When he says this you can just see Bebe's hands in the shot and they are clasped together. In the next shot they are instantly quite far apart.
Liar! Liar! - S4-E10
Continuity mistake: At the beginning of the show, we see Marty add some beer to his champagne glass until it's almost full - just then Bulldog grabs his SeaBee award from the coffee table and now Martin's glass is almost empty, even though he's had no chance to even take a drink.
Continuity mistake: Marty throws his coat on the stairs, but it moves to the landing.
To Kill a Talking Bird - S4-E14
Visible crew/equipment: After Frasier starts the fireplace and it scares Niles' bird, you can see the hands of a bird handler by the stairs on the upper right of the screen. (00:12:21)
Answer: Nanny G (Nanette Guzman - played by Laurie Metcaf) has been a children's entertainer for twenty years, and tells Frasier, "Do you know what it's like to play the same character for 20 years?!" The joke is that Kelsey Grammer has been playing Frasier Crane since 1984, when the character first appeared on "Cheers", so Kelsey in real life has been doing just that!
Super Grover ★