Continuity mistake: In one of the sequences where Niles and Shenkman are running in and out of the bedroom, Shenkman sprays perfume around the bed. The roses that were on the pillow have now completely disappeared and never reappear although neither Niles nor Shenkman touched them.
Continuity mistake: At the very end of the show, when Frasier, Niles and Martin are on the balcony, all three have their hands and arms folded in front of them, leaning on the railing. The shot then goes to behind them, and Frasier is standing with his arms straight out, and only his hands on the railing.
Continuity mistake: At the end of the show Frasier, Niles and their dad are having drinks and Niles goes to top off Marty's shot glass - but just as he pours the drink, Martin pulls it away. In real life the drink would have ended up on the floor, but the scene continues as Niles keeps pouring into the glass.
Continuity mistake: When Frasier, Marty, and Niles are having drinks at the end of the show, Frasier says "I think we have a 3-way tie" and we see Marty holding his drink in his left hand - the shot then switches and it's suddenly in his right hand, with no time for a natural change.