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: 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.
Continuity mistake: When Frank forces Melvin to take in Verdell the dog (just after Simon has been beaten up), the camera follows Verdell as he explores Melvin's apartment alone. Melvin's grand piano at this stage has the lid open, but does not have the music rest up. Shortly afterwards, Melvin re-enters the apartment, prepares food for the dog, places the bowl on the floor in the sitting room, then walks over to sit down at the piano. Suddenly the piano's music rest is up. There is no way Melvin has had the time or opportunity to do this during this sequence.
Continuity mistake: When we see Simon in hospital after being badly beaten up by the thugs, he has long, similar stitches over his face and also over the bridge of his nose. When he is released from hospital most of the cuts have left very visible scars of almost Frankensteinian quality, only the injury on the nose is hardly visible. At the end of the movie, for example when he is talking to his parents over the phone, his nose is now unblemished while the other scars still look quite frightening. (00:30:25 - 01:47:00)