Continuity mistake: As Kirby is showing Roz his prom pictures, she sees the picture with his hand on her behind. In the scene her hair on her right changes position in the following shots from on her chest, to slightly behind her shoulder, to completely behind her shoulder.
Continuity mistake: As Marty says "Claire says", he is holding his sandwich is both hands. As Daphne turns towards him and says "shut up", he is holding the sandwich in his left hand and his right hand is on the arm of his chair. There was no time for the switch.
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.