Continuity mistake: For "Crock Tales" (11x22). In the 2002 flashback Niles and Daphne have just slept together. Actually they first had sex in 2001.
Goodnight, Seattle (1) - S11-E23
Revealing mistake: You have to be very quick to spot this, but when the cannon goes off Niles drops the ring, you can actually see it drop between Eddie and the camera and bounce away from Eddie. In other words, it certainly doesn't go anywhere near the pate.
Goodnight, Seattle: Part 1 - S11-E23
Continuity mistake: (This is for "Goodnight Seattle.") When Eddie is eating the pate with the ring in it, in the wide shot we see that he's finished all the food and is licking the plate clean. It then cuts to a closeup, and the plate is suddenly full of food. Back to the wide shot, and he's licking a clean plate again.
Goodnight, Seattle (1) - S11-E23
Continuity mistake: When Daphne, Niles, and the vet are in the examining room the items on the table in the foreground change positions in different shots.
Goodnight, Seattle: Part 1 - S11-E23
Visible crew/equipment: (This is for the last episode, "Goodnight, Seattle.") When Kenny opens the door to use Frasier's bathroom, you can see a light pass across the wall above the fireplace.
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: It equals the record of James Arness of "Gunsmoke" for the actor who's played the same part on TV NOT in a soap opera. If you include soaps there are two main contenders - William Roache, who's been playing Ken Barlow in "Coronation Street" in the UK since 1960. Don Hastings has been playing Robert Hughes in US soap "As the World Turns" since 1960 as well.