Continuity mistake: In the scene where Ace is trying to figure out the Finkle/Einhorn connection there is, what looks like, an air horn on the far end of the table to the right of the dog. A shot or two later when it shows the dog's hair around the picture of Finkle you can see the end of the horn laying right next to the dog on his left side.(This is visible in the screen shot already on the site that shows the dogs hair position changing.).
Continuity mistake: When Ace is dressed as a HDS delivery man, he starts playing soccer with the package he is carrying. After that you can see that the box is open at the top. When he is at the door, you can see that someone has put new tape on it to close it again.
Continuity mistake: At the end, when Ace embraces Melissa, the position of his arms changes.
Character mistake: Ace claims the stone he found is triangular cut Orange Amber from a 1984 AFC Championship Ring. The stones in the actual 1984 AFC Championship Ring were not triangular cut Amber, they were round cut Diamonds.
Continuity mistake: When Ace empties the filter from the water tank, he blows dirt off his hand to get a better view of the precious stone. He does not, however, remove all of the grime off his palm. In the close-up shot of his hand to visualise the stone, his hand is clean.
Continuity mistake: Melissa says 'Why did it have to happen now, two weeks before the Superbowl?' She later says to Ace that it is Superbowl Week, and that someone stole Snowflake last night.
Other mistake: The band Cannibal Corpse is falsely credited as "Cannibal Corpses" in the end credits.
Revealing mistake: When Ace is at the mental hospital and slams his face down on the bench, you can see the actor playing the doctor begin to laugh before the camera cuts away to a front shot of him and Courtney Cox.
Continuity mistake: When Ace rummages around in the filter, his hand gets dirty as he grabs hold of some stuff. When he blows the muck away, and is left with just the gem, it is completely spotless.
Continuity mistake: When the people take the dolphin and put it in the truck near the beginning, they close the truck door and the door is red. When it shows the truck driving away, the door is white. (00:07:15)
Revealing mistake: When Ace and Courtney Cox are kissing in the stadium, you can see the cardboard cutouts in the upper deck (replacing live fans).
Other mistake: When Ace goes into the death metal club two people stop moshing and very obviously look at the camera smiling straight at it.
Factual error: The movie that Ace plays back when he goes to Finkel's house mentions that it is Superbowl 17. Only problem was the entire film references to Super bowl 19 between the Dolphins vs 49ers. Superbowl 17 was Dolphins vs Washington. Added to this the Dolphins lost by much more than just a field goal in both games.
Deliberate mistake: In the final stadium scene, the scoreboard sets forth that it is the 2nd quarter, 3rd Down and 6 yards to go. The game clock indicates that 15 minutes are left in the quarter. The announcer indicated that it was the start of the 3rd quarter, and neither team kicked off.
Continuity mistake: After Ace tells Lois Einhorn about Ray Finkle and she steps out of the bath room to sit behind her desk. Pay attention to the filing cabinet to her left. The folders go from organized up right to being on their side.
Other mistake: When Emilio is rummaging through Einhorn's desk drawers, he finds a note from Roger to Einhorn, thanking her for a wonderful evening, and saying that he'll see her on Friday. When Emilio calls Ace, he says that the note says that Roger was thanking her for a wonderful Saturday evening. He never wrote down what day the evening was on. It never said Saturday anywhere on the note.
Continuity mistake: Ace gets the call about Einhorn's date around maybe 10 or 11pm. When he's in his bathroom there's a window with the light coming through like it's morning or early afternoon.
Suggested correction: He's in the bathroom after a whole night of thoughts about connection of Einhorn and Finkle. The movie makes it very clear that he spent many hours trying to solve the case, of course it was morning already when he figured it out.
Continuity mistake: When Einhorn is tossed into Snowflake's crudely constructed holding pen at the docks, the dolphin seems to have disappeared.
Suggested correction: When she falls in the water, the dolphin is visible right near her in plain view.
Continuity mistake: When the man is sitting by a chess board and Ace is talking, as the camera direction moves between characters the chess pieces on the board suddenly disappear and don't return.