When Ross first sings the song to Emma his hand is on her back, in the next shot it's under her head and then on her back again.
No one would've have been able to take the SAT's for Rachel because everyone has to show valid identification before they take the test.
When Joey and Chandler are watching Richard and Monica's sex tape, Monica walks in. When Joey pulls her down on the floor, you can see a knee-pad strapped to her leg.
When Joey and Chandler are watching the sex tape from Richard's apartment, it starts off as a football match - which is visible when the camera is pointing towards tot he TV. When the video "switches" to Richard and the other girl having sex and the camera angle switches to looking towards the TV, the TV is blank. Obviously they won't show a sex tape in Friends (1994), but you would think they would avoid showing a blank TV screen.
When Chandler and Joey are watching the tape found in Richard's apartment, the TV is initially on and showing a football game. However, once Chandler walks to the kitchen, we see that the TV is off, even though sound from the TV is still occurring.
When Joey is in front of TV to check what's in the tape, he switches TV on by touching the top of the TV. However, it's on/ off button is visible under the screen.
When Chandler is happy the sex tape is just a football game and says he's going to get a beer, a safety mat can be seen to his right, the viewer's left, by the door where Joey will tackle him to the ground moments later.
The real estate agent is legally prohibited from disclosing to Chandler why Richard was selling his apartment because this is considered privileged information.
In this episode, Monica says that Chandler is jealous of Richard because Richard has a mustache and Chandler can't grow one. This is incorrect because Chandler had a goatee earlier in the series.