Continuity mistake: When Simon comes to Melvin's apartment to tell him that he has found his dog and Melvin tells him not ever to knock at his door, not even when the smell of a decaying body is emanating through the door so that he has to put a hanky to his face because of the stench, the glasses he is holding in his right hand disappear and reappear between shots. (00:07:20)
Continuity mistake: In the scene where Simon is sketching/drawing Carol, he rips off the hand piece of his cast so he can move his hand freely. When they are getting out of the car once they get home, you can see that the hand piece of cast that Simon ripped off is back on his hand and the cast is undamaged. (01:49:30 - 01:54:40)
Continuity mistake: In the hospital, Jackie goes to give Simon her mirror so he can look at himself, and her green purse is scrunched up under her arm. As the shot changes to a wider angle, the purse is now hanging over her stomach.
Continuity mistake: When Carol enters Melvin's building soaking wet to tell him she'll never sleep with him, we can see bra straps across her back under her blouse. But at Melvin's door, she's embarrassed to discover that the wet blouse reveals a distinct lack of a brassiere.
Continuity mistake: In the first diner scene Melvin sits down and takes off his glasses. He starts fiddling with the button of his breast pocket. When the camera angle changes his hands are somewhere else and the pocket is still buttoned. When it changes again he is putting his glasses into the now unbuttoned pocket. (00:12:20)
Continuity mistake: When we see Carol writing the thankyou note, the page is numbered (23), there are 8 lines of writing on the page and she says she is on the last page. When she is looking up the word 'conscience' in the dictionary, the paper is visible again but it is a different sheet - there is no number and there are only 4 lines of writing. It is the page she is about to write on because the last words written are 'have it on my ' - 'conscience' following this phrase makes sense. (01:09:00)
Continuity mistake: When Melvin goes to the restaurant after seeing the psychiatrist and is not served by Carol he bangs on the table and tells the waitress to go and get her. The flowers in the vase on the table change twice in consecutive shots. Pre-bang = yellow, orange and red. Post-bang 1 = white, 2 yellow and red. Post-bang 2 = 2 white and 2 yellow. (00:41:40)
Continuity mistake: When Melvin gets up to go give Simon some Chinese soup, the clock reads 3:22am. The next scene in Carol's apartment is supposedly later on the same night, yet the babysitter has just arrived, her child is still up, and she and her mom are getting ready to go out for the night (even telling the babysitter that there's pizza in the freezer they can cook later). We know it is supposed to be the same night because in the ensuing scene, Frank tells Melvin he heard he "brought Simon chicken soup last night." (01:04:25)
Continuity mistake: On the trip to Baltimore when Carol tells Simon to wait to tell his story until she pulls over, the top of the car is down. When she's pulling over, the top is up.