Continuity: There was an episode in which Martin attempts to end a feud between Frasier and Niles by telling a story about his detective partner. He starts with the line, "I never had a brother...", but in the episode about Frasier's cousin Nikos getting married, Martin's brother Walt was introduced.

Continuity: Frasier is based on the character originally created on Cheers. In Fraiser, he lives with his father who is a retired police man. On Cheers Frasier once mentioned his father was a scientist. It's also worth noting that in one episode of Cheers John Mahoney, who was to later play Frasier's dad, turns up as a pianist. [Frasier also said on "Cheers" that his father was dead. When Ted Danson made a guest appearence on "Frasier" Frasier admitted that he had lied about his father since the two had been arguing so much.]

Deliberate "mistake": The background of the street scene from Frasier's apartment balcony shows cars and other vehicles but they are always standing still.

Continuity: Across the show, Marty is supposed to be about 21 years older than Frasier (he turns 65 in season 5). There are at least two problems with his age - Frasier is supposed to have been born in March 1952 and in Season 5 (Roz and the Schnoz) Marty mentions going on shore leave as a single guy in 1952. Even if he was confused about the year, Frasier didn't call him on it. He must have done just a short stint in Korea as he was already a cop when he met Frasier's mother - they met at a murder scene, and he must have been 20 years old at the most. She was already a full fledged psychiatrist.

Continuity: Early in the run of Frasier, Lilith arrives in Seattle for a visit. Niles is very cold with her, as he claims she laughed at his wedding vows. Niles had been married to Maris for 15 years when they separated during the 3rd or 4th season. How then could Lilith have been at their wedding? At that time Frasier would have not have even known Lilith, and was probably involved with Diane Chambers.