Continuity mistake: In the conference room, Frasier says, "I just said that," and the shot shows his arms resting on the table with his hands up, gesturing. The next shot, from the side, shows him leaning back in his chair with his arms right off the table. The shot then goes back to the original position. There was no time for him to move naturally.
Continuity mistake: When Bulldog gets back to the kitchen table after closing the door on Roz's date Ted, there is a large blue casserole dish sitting there - it wasn't there when he went to answer the door. Roz had been hiding the whole time, so she didn't put it there.
Continuity mistake: Near the beginning of the show, Frasier brings Roz a muffin in a bag which she places to the left of her phone (her left). During the scene, the bag shifts from being near the console to being back to left of the phone. At one point Frasier and Roz leave the booth, then come back in, and it has moved in the meantime.
Continuity mistake: Frasier and Martin are in the kitchen and Marty gets some chips out of the cupboard next to the fridge. As he leans down to pet Eddie we can see a bag of blue chips still in the cupboard - but when he straightens up to talk to Frasier, we see a red bag in the cupboard, not the blue one (the camera angle remains the same).
Continuity mistake: Frasier is sitting on the couch watching Wheel of Fortune and eating, with a plate on his stomach. As he talks to Niles he places the plate on the coffee table. Niles says "Are those profiteroles?" and Frasier gobbles them up. Then we see Frasier put the plate on the table again.
Continuity mistake: Frasier (and later the others) come back to his apartment to avoid the rain - they shake off umbrellas, and we even hear the storm at the very start of the scene. However there's no rain on the balcony - can't be covered, as we see in "call me irresponsible" during the obligatory sex scene that when it's raining the balcony gets soaked.
Revealing mistake: About 1/3 through the episode, they are in Roz's apartment. If you watch when people enter or leave the apartment, the door has a handle lockset. It also has a lock cylinder about 1 1/2 feet above it on both sides of the door. The problem is, the side of the door has no drill hole where the latch assembly should be: it's just solid wood. The lock isn't attached to anything that would enable it to work.
Revealing mistake: In the scene where Frasier and Lilith meet in the living room, where Frederick has created a romantic atmosphere, Frasier has a long speech about how Lilith is not going to get him back, ending with "I need to be finessed!" and Bebe Neuwirth goes out of character and begins to giggle, before she quickly covers her mouth and pulls herself together. Though Lilith might have found Frasier's comment amusing, it would definitely not be in character for her to giggle like that.