Shortly after John O'Malley's accident near the end, when Sam looks out across the stage at Dulcinea dancing, you can see the figure of Nicole standing on the opposite side of the stage (wearing a pink dress), but she is supposed to be on stage playing Dulcinea. This was obviously taken from an unused scene shot during the first performance at the beginning of the episode, with Michelle in the role of Dulcinea and Nicole watching in the background.
May 24, 1979 is said to be a Sunday. However, it was actually a Thursday.
Sam says he had a crush on his piano teacher when he was 15, but in Blind Faith - February 6, 1964 (1989) he couldn't play piano.
Sam was able to play the piano in that episode once Al supplied him with sheet music. Not a goof: due to his "Swiss cheese memory," Sam did not remember that he had played piano at Carnegie Hall when he was 19 years old.
Immediately after Sam leaps into the body of Ray Hutton (the understudy of the actor who portrays Don Quixote), the female makeup artist doing his makeup has a lit cigarette hanging from the left side of her mouth. Her reflection in the mirror also has her cigarette on the left side of her mouth. If it was actually her real reflection in the mirror, the cigarette would be seen hanging from the right side of her mouth, because the mirror would flip the image. What is shown is actually the same actress who moves behind the camera and over to the other side of a fake mirror, while a double's hands are placed on Sam's shoulder. Like the cigarette, the actual actress's hair isn't mirrored, obviously there wasn't time to change these details the way the shot was set up.
Manny reads a newspaper with the headline "Transit Strike Over." However, the New York City transit strike did not begin until April 1, 1980, more than ten months after the events of this episode.
When Paul Sand is hollering the seconds at the beginning of the episode he says 47 seconds - the next thing he says is 43 but his mouth is saying 48.