Factual error: In the begining at the bridge ceremony, the band plays Manhattan Beach by John Philip Sousa. However, Manhattan Beach was composed in 1893. (00:00:50)
Continuity mistake: When Stuart is on the phone with Kate and tries to explain who Leopold is and why he is with him, the clock on his wall moves back by about two minutes when she sits down. (00:13:25)
Continuity mistake: In the first heated discussion between Leopold and Stuart a pen suddenly appears behind Stuart's right ear. (00:17:15)
Factual error: The morning after Leopold and Stuart travel to the present, the two of them are talking about why Leopold followed Stuart to the bridge. Leopold mentions that he was afraid Stuart might be Jack the Ripper, whose first murder was in 1888, twelve years after Leopold's time. (00:17:55)
Continuity mistake: When Leopold leaves the apartment with Bart, the leash roles itself up in several loops between shots. (00:23:20)
Continuity mistake: When Bart lays a turd at a tree, the leash is wrapped tightly around the trunk holding him back, but after he is done he moves on forward, while the leash disappears at the top of the frame. (00:25:00)
Continuity mistake: In the board meeting scene in which the margarine commercial auditions are first being looked at, the video gets paused on the first man auditioning and then the second man auditioning, but in each subsequent shot of the television, it's back to being paused on the first man auditioning. (00:29:49)
Other mistake: On the first day at Stuart's apartment Leopold wears some green 19th century trousers he wasn't wearing during his time travel, and which surely weren't part of Stuart's wardrobe. (00:30:05)
Factual error: Leopold recognizes the telephone as the "talking telegraph" he saw at a fair "last year" in the scene where Stuart calls home from the hospital. The first public showing of the telephone was at Philadelphia Centennial Exposition which opened in May of 1876. (He is from April of 1876.) That aside, if he saw a talking telegraph in 1875, it would've been quite a feat because inventor Alexander Bell submitted his patent in 1876. (00:30:15)
Continuity mistake: Hector, the little boy who spends his afternoons at Stuart's place watching TV, is eating from a bag of 'pirate booty' in his lap when Leopold sees him. When he offers Leopold some, the bag is suddenly next to him on the sofa. (00:31:10)
Factual error: It's not just the date of La Boheme they have wrong. Pirates of Penzance didn't premiere until 1880 and it was the apprentice who found love with the Major General's daughter and not, as stated, the Pirate King. (00:33:00)
Continuity mistake: At the dinner at Kate's Charlie stands up to prove his manners. His fork is empty, but when we see him standing there's some food on it. (00:37:20)
Continuity mistake: During the dinner at her place Kate has both her sleeves pushed up to the elbows, but after she takes some dishes to the kitchen there's one brief shot from behind where the right sleeve is pulled down. (00:37:40)
Continuity mistake: In the hospital Stuart tries to grab his neighbor's phone. When he detaches him from his life support and alerts the nurse he holds the receiver in his right hand. The camera changes to a shot from behind, and he picks up the receiver again with his right hand. (00:39:50)
Continuity mistake: When Leo and Charlie are on the street talking (just before they interrupt Kate's dinner with JJ), Charlie has a cell phone and napkin in his hand, but from one angle it disappears, then reappears in the shot (from a different angle). (00:56:20)
Continuity mistake: When Charlie and Leopold are walking home after they go to the bar, Leopold says it is after midnight and they should go home. The next scene is back at the restaurant with Kate and J.J. When the camera is on J.J., you can see his watch and it says it's 9:30. (00:57:00)
Continuity mistake: When Kate comes back home after the punctured dinner with J.J., her hair is freshly done. Even if she had ample chance to do this, it's out of the question that the rather messy style she had chosen for the dinner was not intentional on such an important occasion, and there was no reason to change this afterwards. (01:00:25)
Continuity mistake: Leopold tells Kate that by his 30th birthday he had "become a blemish on the family name", meaning he must be at least 30 in 1876, making his birth year at least 1846. When he goes forward in time to 2001, he is said to be at least 148 years old, making his birth year 1853 (2001-148) which would make him 23 years old. (01:11:45)
Continuity mistake: When Kate is on the top of the roof with Leopold eating dinner, you can see her dress has straps on her shoulders. When the camera shoots back and forth from Kate to Leopold, you can see that the strap has fallen off her shoulder and shows her bra strap. However, when they go back to Kate it is back on her shoulder. (01:12:00)
Continuity mistake: When Kate tells Leopold that her Sundays are spoilt because the day after is Monday, she cuddles herself against his chest twice in successive shots. (01:21:10)
