Continuity mistake: During the part of the show where they are getting ready to play Murder we can see empty punch glasses on the table - in another shot we see three even though no one went near them. This changes back to 2 after the lights come on - unlikely anyone helped themselves to punch when the lights were out.
Continuity mistake: Kenny enters the booth, and Dr. Nora's purse is on the edge of the desk. Immediately in the next shot it's gone. Then it's back. When Kenny leaves it's gone again. (00:10:25)
Continuity mistake: Near the end of the show, Niles and Frasier are shaping hamburger patties in the kitchen. Niles has a blue bottle of water which sits on the stove top in front of him. In one shot it suddenly appears on the counter to his right; even though Niles hadn't moved it. By the end of the scene it is back in front of him on the stove top.
Continuity mistake: Near the start of the show, Roz arrives at Frasier's with baby Alice. She is standing near the balcony door in her black gown when suddenly a white spit-up cloth appears on her shoulder that had not been there previously in the scene.
Continuity mistake: When Frasier and Niles are in the restaurant, Niles is under the influence of medication. He lays his head down on his arm just as one of the geniuses arrives and greets them. In the next shot, his head is lying right on the table, with no time for him to have switched positions.
Audio problem: Dr. Nora's mother is pounding on the glass of Frasier's booth. She then wags her finger at Nora but the sound of her pounding continues, even though she's no longer doing it.
Continuity mistake: When Dr. Nora's mother comes into Nora's booth, she locks both doors so Frasier can't get in. However, Nora gets upset, quickly gets up and opens the door, without having to unlock it.
Continuity mistake: Near the end of the show, Dr. Nora's mother is chasing Nora through the corridors of KACL, behind the windows of Frasier and Roz's booth. We can see them go by, from window to window. The shot then cuts to Frasier, looking horrified, and we see Nora's mother run by a couple of windows again - even though this could not possibly have happened in real time.
When a Man Loves Two Women - S6-E21
Continuity mistake: Niles is trying to convince Frasier to play squash - he has his hands on the back of Frasier's chair. Cassandra comes out of the kitchen and we see one of Niles' hands on Frasier's shoulder. In the next shot, both hands are back on the chair, even though there was no time for this to happen naturally. (00:02:35)
When a Man Loves Two Women - S6-E21
Continuity mistake: Daphne and Marty are arguing about Cassandra and Faye. As the shot goes from one to the other, the spout on the milk carton goes from opened to closed and back again. (00:09:35)
When a Man Loves Two Women - S6-E21
Continuity mistake: During the scene where Niles is flipping a coin, the newspaper on Marty's lap is sometimes opened flat and sometimes folded over, even though he doesn't touch it. (00:09:50)
When a Man Loves Two Women - S6-E21
Continuity mistake: Before Frasier says "Enough, Dad!", we can see a spoon in Marty's cereal bowl. In the next shot it's gone. (00:10:15)
When a Man Loves Two Women - S6-E21
Continuity mistake: When Frasier is in his apartment talking to Niles, Marty, and Daphne about choosing between Cassandra and Fay, the milk on the breakfast table changes position several times - from behind the coffee pot and near Daphne to the other side of the coffee pot in front of Martin.
When a Man Loves Two Women - S6-E21
Continuity mistake: When Frasier and Fay are at her place talking on the couch, there is a throw that sometimes is at the end of the couch on the armrest and sometimes is on the back of the couch, behind Fay.
When a Man Loves Two Women - S6-E21
Continuity mistake: When Frasier and Niles are in the cafe, Niles says "So what was Fay doing at your apartment last night?" When he says this, you can see he has just started to stir his coffee with a spoon. The shot then changes and the spoon has vanished.
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.