When Harry shows Bobby DiLea the box of money, all the cash is rubber banded into neat piles. Later Harry shows Moe the same box and the cash is loose and there doesn't appear to be as much in the box as earlier. Then, when Harry and Moe go down to the casino, the money is in neat piles and the box is filled up again.
After Harry and Moe have the Cadillac painted pink, you can see the scrape marks on the passenger side of the vehicle before they scrape it on the guardrail.
When Moe and Harry arrive at Resorts International in the damaged Cadillac, the longshot shows them hitting the corner of a parked car and the Resorts doorman running to inspect the damage. In the next shot, he is still at the door.
When Bobby DiLea shows up at the hotel room, Moe is in the hot tub getting his hair washed, but in the next shot he is at the door completely dried off and wearing a red robe.
After Harry is shot, the bloodstain on his shirt gets smaller as the scene progresses.
The title characters bet on a thoroughbred horse race at The Meadowlands Racetrack but they are reading from a program that is strictly designed for harness racing since The Meadowlands is primarily a harness racing track.
When Harry is at the bar and takes the towel to remove the tropical tan lotion, a quick shot before he wipes his face shows the makeup is already gone. Also, there is no makeup on the white towel he used.
When Harry stands by Costello's car right before it explodes, you can tell that it is a process shot or he is standing in front of a rear projection screen.
When Moe accidentally hangs himself from the light fitting, the metal loop on the back of his concealed safety harness is clearly visible for a split second when the camera looks down at him from above.