Continuity mistake: The water level in the dispenser rises and falls by itself several times throughout the episode. (00:08:05)
Revealing mistake: In the close-up of Frost's hand while the doctor is stitching up his wound, you can see the delineated edges of the latex make-up patch used to simulate the injury. (00:12:30)
Continuity mistake: In 1912, Ray writes his letter in pencil. When it's delivered to Melissa in 1986, it's written in black ink. (00:20:15)
Time and Teresa Golowitz - S2-E18
Continuity mistake: As they talk, Prince and the pianist stand beside the apartment wall that's covered with Broadway show posters. There's no break in their conversation, but when the shot cuts, they're across the room in front of the window. (00:03:15)
Song of the Younger World - S2-E20
Factual error: It's the 1800s, but Amy's skirt has a 20th Century zipper running down the back. (00:05:15)
Song of the Younger World - S2-E20
Factual error: The 19th Century reformatory has modern electric light bulbs hanging from the corridor ceilings. (00:21:10)
Answer: Poisoned food, heart attack from eating too much food, or he slipped in the shower. The list is endless.