The barbershop quartet was called the 139th Street Quartet and two of the members, Douglas Anderson and James Kline, returned in the Season 8 episode The Stork Brings a Crane.
In reference to above posting, if you look closely you'll notice that as Diane moves toward the door...in the dark you can see that the cabinet is still in front of the door. The scene then cuts to Sam's reaction to her line of dialogue, and when the camera cuts back to Diane, as she turns on the light, the cabinet if back in its proper place. The assumption is that Diane moved the cabinet right before she turned on the light. We didn't see it because of the way the scene was edited. She moved it when the camera cut to Sam.
In the hospital room, when Diane visits, Sam turns the lights off and pushes a dresser infront of the door to "stop" anyone from "accidently" walking in, however when Diane refuses his advances, and goes back to the door to leave, turns on the lights, and the dress magically has been replaced to it's original location!
(Sam is putting the moves on Diane while she is giving him a pep talk on aging.)
Diane: Oh, Sam, this is wonderful. An old person wouldn't be doing this. This is the act of a vital, strong, young man. Who wants a woman. Who wants sex. (Sam gets too close) Who won't GET it...
Diane: Pretty girl, Sam—be careful she does't loose a baby tooth giving you a hickey.
Carla: Sam Malone never ages. It's one of life's great truths. Let me tell you something Sammy, when you're 87 you'll still be a hunk to me. Of course I'll be senile and blind.
Sam: And pregnant.
Carla: Yeah, probably.
Sam: The day you start accepting getting old is the day you get old.
Cliff: Guess what I've got in the bag.
Carla: What's left of your mind.
Woody: You know I love barbershop quartets. You mind if I make a little request.
Singer: Not at all.
Woody: Could you give me a little trim around the ears later?
Diane: Does Sam's behavior give you pause? Methinks the man doth protest too much.
Woody: Excuse me, Miss Chambers, but shouldn't it be "I thinks"?
Carla: Not in your case, Woody.
Diane: My worst fears are confirmed.
Carla: There's been a peroxide embargo?
Diane: Methinks the man doth protest too much.
Diane is paraphrasing the line from Hamlet: "Methinks the Queen doth protest too much."