And the Dish Ran Away with the Spoon (2) - S8-E2
Continuity mistake: At his "reception" Niles has his arm around Mel and says, "I didn't even have to check her teeth" to a member of the horsey set - and the shot then shows Mel and Nils standing apart, even though there was no time for them to have done this.
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.