Continuity mistake: Tyler was given a pat-down before going into Derek's room, and he did not have a cell phone in any of his pockets, yet he was able to produce a cell phone to show Derek a photo. (00:16:05 - 00:18:53)
Continuity mistake: When Derek (as Tyler) goes into the hallway and when he walks outside toward the SUV, no cell phone outline can be seen in his front pockets. Somehow, he has Tyler's phone (or a different phone) when he gets inside the SUV. (00:20:15 - 00:20:45)
Plot hole: Derek, who escaped the mental hospital by pretending to be his twin brother Tyler, was able to locate Tyler's vehicle by using the keys to beep its horn. Once inside the SUV, he apparently found Tyler's cell phone, which is odd because most people carry their cell phones with them. But Derek did not ask Tyler for his cell phone's password before rendering him unconscious - so how did he gain access to the cell phone without the password? (It isn't likely that Tyler previously gave it to him). (00:20:40)
Suggested correction: Tyler never left his cell phone in the car. He had with him when visiting Derek. We see him pull out his cell phone to show Derek a picture, so the phone was already unlocked, assuming he locks it with a password in the first place.
I haven't had time to finish posting the rest of the mistakes I have, but I just uploaded two that should show up under "pending submissions." They probably should have been posted before the one above. I suppose the real question is where the cell phone came from each time.
Other mistake: Derek changed into Tyler's clothes to escape the hospital and take on Tyler's identity. However, it does not look like he remembered to put his blue hospital ID band onto Tyler's right wrist. Hospital bands are usually securely on and not easily removed (or removable without breaking them). When the nurse was removing Derek's (actually, Tyler's) wrist restraints, there was no blue hospital ID band on his right wrist. He asked, "How do I prove to you who I really am?" (No ID band!). (00:21:30 - 00:24:37)
Revealing mistake: One actor played the roles of the twins. At the mental hospital, there were subtle but noticeable differences between the way Derek's bangs were combed to the right (flatter with no loose ends sticking out) and he had a small section of hair raised near the back of his part. When Derek left as Tyler, he still had Tyler's more jagged bangs and no raised section of hair near the back of his part. It's against the odds that the twins would have the exact same facial hair/haircut on visiting day. (00:17:45 - 00:20:20)
Continuity mistake: There's a vase of yellow flowers to the right of the helium "Happy Birthday" balloon (and screen). When Ashley gets up to answer the door, she walks past the balloon and the vase of flowers should be visible but is not. (00:01:40 - 00:02:28)
