Merry Christmas, Mrs. Moskowitz - S6-E10
Continuity mistake: The same mistake happens throughout this scene - Helen has her purse on her arm and then on her shoulder and then back to her arm from shot to shot.
Merry Christmas, Mrs. Moskowitz - S6-E10
Continuity mistake: Niles and Marty are in the kitchen and Niles is coaching Marty on how to pretend to be Jewish. While they are talking, the lid on the sugar bowl goes from being on properly to being askew, even though no one touched it.
Merry Christmas, Mrs. Moskowitz - S6-E10
Continuity mistake: The first time Helen and Faye try to leave, Helen tucks her purse under her left arm but in the next shot we see her move the purse from her right to her left arm again.
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.