Other mistake: In the scene where Frasier is in line for tickets for Roz he is talking to Lana on the phone and asks if he can move Kirby's tutoring up "tomorrow" to four right after school because he made plans with Claire later that night. You can see on the sign next to him that the tickets go on sale Saturday morning and Roz had previously said in the beginning of the episode that she wanted to start standing in line Friday so she would be first in line Saturday morning. So it is obvious that Frasier is in line Friday night which would mean tomorrow would be Saturday, which means Kirby being in high school would not have school the next day (Saturday) like Frasier said. (00:21:05)
Continuity mistake: Frasier is at the restaurant trying to stop Lana from going to talk to Kirby. She has her purse under her arm but the next shot shows her holding it by its strap.
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.