In all games, the couch will be shown dancing inside Darkness's living room and will remaining dancing while Sam has not actually entered the living room. When Sam does enter all the furniture jump back into their proper places and remain stationary.
In the Darkness' living room storyline, Sam's mask is in the center of the living room with the dancing furniture. However Sam can't get the mask when he enters as the dancing furniture will jump back into place and pretend to be inanimate, causing the couch to step down on the mask and prevent Sam from taking his mask back (he can't ask it to get off his mask because it will pathetically try to fool him into thinking it's inanimate). With the help of an invisibility potion from Darkness' laboratory, Sam is able to sneak past the furniture and take back his mask without the furniture seeing him.