When Rachel and Ross are talking near the end of the episode, the bottle of glue on the table behind them is standing up, then is on its side, then is standing up again.
Ross, Joey, and Chandler go on a ride-along with Gary in his police car. According to NYS law, the driver and the front seat passenger are required by law to wear a seat belt. Yet neither Gary, an NYC police officer, nor Ross, who starts out in the front passenger seat, are wearing one. Neither are Joey and Chandler in the back seat.
When Rachel is in Ross' apartment, Emily calls. Rachel heads into the kitchen as the phone is ringing and the swinging door closes normally behind her. After Emily starts talking, at about 6 minutes and 25 seconds into the episode, Rachel exits the kitchen with a blender and bottle of tequila in her hands. This time, the swinging door does not close all of the way. The camera slowly pans a little toward the right to center more on Rachel and the door can no longer be seen.
In the interlude after Rachael has taken the tequila from Ross' apartment, there is a electronic billboard advert for "Mary Shelley's Frankenstein" "coming this November". This episode was released in 1998 but Mary Shelley's Frankenstein was released in Nov 1994.