Something occurred to me last night and I rewatched to check the dream sequence after the self-catheterization.
As we all know, they flopped the film so that everything would feel a bit off without our really knowing why. Once you know, you can see backward words and other signs. But one thing that the super-observant House-freaks wouldn't have missed would have been House limping on his left leg so HL switched that for most of the sequence -- but left it in for just before they revealed it was a dream.
It starts at about 33:50. House is standing in the doorway to the lounge. He has his cane in his "left" hand and is leaning on it. His "right" hand holds the TV remote. (He was standing normally and when the film was flopped, it was wrong.)
House tosses the remote, switches the cane to his "right" hand and limps out. To do this, HL had to limp on his left for the shot.
Pacing in his office during the DDX, he again has his cane in his "right" hand.
But, when they get paged to the POW's room, House opens the door with his cane-less "right" hand and limps in leaning on the cane which is apparently on the wrong side. So HL was limping normally here and it showed up as backwards when the film got flopped.
In the tighter shots it also sometimes appears that he's lurching backwards but that might be my imagination.