Goodnight, Seattle: Part 2 - S11-E24
Character mistake: Frasier says, "it's only an hour flight to San Francisco..." Seattle to San Fransisco is two hours minimum.
Goodnight, Seattle (2) - S11-E24
Continuity mistake: When Eddie eats the wedding ring at Martin's wedding, there's no food on his plate, next shot there is.
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 ★