Frasier is telling the others about what gifts he has for them. In the close-up shot on the others as they listen, the lights on the mantel behind them are blinking. In the wide shot, they are not and the colors are different.
(At 00:01:53) Frasier opens the cupboard door to put the nutmeg jar back just as Martin drinks some of his eggnog and starts coughing. The camera then cuts to a closeup of Frasier looking at the jar, and the cupboard door is closed and Frasier opens it again.
Frasier suggests a vocal distraction, sliding up an octave while descending into a crouched position. Niles suggests the reverse is true, but instead of performing the opposite, he does exactly what Frasier is doing.
After Albert asks the mother in the elevator, 'Haven't got a gas stove up there, have you?', Niles can be seen to speak but there is no corresponding audio. According to the published script for the episode, he says, 'Shut up, Albert'.
(This mistake can be seen in the season five DVD box set [UK release]. In the Best of Christmas DVD collection, it has been edited out.)