When Martin first stops in front of the convenience store the shadow from his car shows it is about noon and it is an asphalt street. In the next shot, the front of the store, the shadows indicate a much later time and the street is full of mud and gravel.
During the microwave bomb scene at the Ultimart, the microwave shows 4 seconds left before the bomb will detonate. It takes 10 seconds for that last 4 seconds to elapse. The microwave then shows "END" just before the bomb explodes.
When Martin is on the landline phone in the hotel room before leaving for the reunion, he hangs up the phone with the cord of the receiver hung on the right. Moments later when Felix enters the room and sees the reunion invitation next to the phone, the cord is hanging on the left.
When Martin kicks down the door in the Miami hotel and shoots the man in the stomach, the slide on his Glock is locked back (empty). When he puts the gun to the mans face the slide is forward and there is another bullet in the chamber.
When Martin gets Paul to help him move Felix's corpse, they take him down some steps which have a solid handrail down the middle of them. In one shot they are both one the same side of the railing, but then in the next (immediately after) Martin is on the other side from Paul.
In the cemetery, Martin removes the cork from the whiskey bottle, leaving some of the foil on the neck. When he upends the bottle, whiskey pours unevenly because the foil is blocking part of the bottle opening. In the next shot there is no foil on the bottleneck and the whiskey pours freely.
When Martin arrives in Grosse Pointe, the NSA agents are following him down Lake Shore Drive. Internal shots of the agents in the car show them driving by the same house twice in the background behind the driver.
While Martin and Debbie are dancing, Arlene Joseph is on the dance floor by the stage. When Felix La PuBelle comes in to claim Sidney Feldman's nametag, Arlene is manning the check-in table. Cut immediately to the next shot, Arlene is back on the dance floor by the stage.
In the restaurant where a woman talks to Blank, she puts her beret on the table and it falls off of the edge off the edge. In a subsequent shot, it has returned to the table without having been picked up.
When Martin first walks into the radio studio, Debi says, "And, here's The Specials, doing... one of their songs." The next shot shows an LP start spinning on a player near a rack of 8 tracks. After that, Debi pushes her chair back from the controls. Right before she goes back, the same player behind her, right next to the 8 tracks, is spinning a completely different LP. To the left of the spinning player is another identical player with yet another completely different LP, but it is not spinning and the tone arm is retracted.
When Martin and Grocer are shooting at the two bad guys at Debbie's house Grocer's pistols both are shown with the slides locked back indicating they are empty. The pistol in Martin's left hand also locks back showing it to be empty but the one in his right hand does not, indicating he has at least one round left in it and he could have shot Grocer.
When the scene cuts back to Martin the pistol in his right hand has changed to show the slide locked back.
In the beginning of the movie, just before Martin sees Debi for the first time, sitting in her radio booth, he is driving in his car and looking to his right. He is wearing a black cap and sunglasses. The camera mounted in the open window of the car, is clearly visible in their reflection multiple times.
When DJ-ing, Debbie plays a Specials LP with the Two Tone Label on it. The song she played, Pressure Drop (originally done by Toots and the Maytals), never appeared on any Specials LPs on the Two Tone Label, but on an album released in 1996 called "Specials Today" on Chrysalis Records.
During the reunion party, Martin takes a photo of Debi holding the baby. He is using a Minox "spy" camera which has no flash, but there is a flash when the photo is taken, as well as the sound of a motor drive that the camera doesn't have either.
In the kitchen at Debbie's house, Blank and Grocer both empty there pistols and the slides lock back. Then they both pull the triggers and all 4 guns "click". Neither the Glock 17s nor the Colt Mustangs can click when the slides are locked back.
The arcade game that the Ultimart employee is playing during the shootout is the aptly titled classic Doom II. The game was never actually available in a commercial arcade cabinet and must have been constructed specially for the film.