Blooper

When Danny drives Julio's Mercedes from the impound lot, it has an obvious rear-view mirror on the windshield. In the close-up of Danny and Ray in the vehicle afterwards, the mirror is not there. In subsequent shots, the mirror is sometimes there and sometimes not there.

At the start of the limo chase, as the limo pulls away from the airport a white Ford Mustang pulls out in front of it. The next shot shows the limo strike a white Plymouth Horizon.

In the ladies' room, the lawyer for Aunt Rose's estate throws his business card into the sink. When Ray picks it up, it is on top of the sink.

When Ray and Danny pick up the taxi, they back into the Pontiac's left rear with their right rear corner. However, subsequent scenes show damage only on the taxi's right front fender. Additionally, when the drug dealer repeatedly fires into the right side of their bullet-proofed taxi there is no damage whatsoever. There would be paint damage, metal dents, and some spider-web cracks in the glass wherever bullets struck the car.

The red 1969 Mustang is splashed with snow on the driver;s side when it swerves to miss the delivery truck. As it crashes in a following scene, the driver's side is clear of snow.

After Hughes and Costanzo call for backup, the police car they enter has "Chicao Police" misspelled on the doors.

When Gregory Hines and Billy Crystal are discussing their shooting accuracy at the getaway vehicle with the men who tried to rob them, Ray says he hit the windshield with all six shots. However, there are only five bullet holes in the windshield.

They were both bragging and trying to one-up each other, not giving the shooting match score.

After Danny and Ray arrest Snake when they let him go, he's at police check-out to receive all his belongings he was carrying around a briefcase with 50,000 dollars in it before his arrest. No police department on the face of the earth would allow someone they just arrested to leave with that much cash, it would have been immediately confiscated upon arrest.

In the mid-1980s civil asset forfeiture was not as prevalent as it was today and was only just starting to become common among law enforcement organizations; with no direct evidence linking the money to a crime, even though they suspect it to be true, at that time there would be no legal reason for the police to confiscate the cash.

Aunt Sophie says to Costanzo "Italians don't get divorced, it's a sin, they're just not together". Italian isn't a religion, it's a nationality. So she should have said, "Catholics don't get divorced, it's a sin". Unless she was trying to imply that all Italians are Catholic. Even if she had said "Catholic" it still would have been a mistake, as it is not a sin to get divorced in the Catholic belief, it's only a sin to get remarried.

While this may be factually true, it is the belief of this particular character that Italians don't get divorced, likely because of the Catholic faith of a vast majority of them.

Costanzo says Key West is as far south as they could get without having to speak Spanish, but the northernmost Hawaiian island is 11° further south than the southernmost point of Key West.

Constanzo was clearly talking about the contiguous United States, of which Key West is the southernmost point.

In the opening scene, Ray and Danny are in a Chicago park at Christmastime. All of the trees in the park are loaded with green leaves - not something you'll ever see in Chicago in December.

The film takes place around the Christmas season, as suggested by the "snow" seen in all of the street scenes. However, it is obvious that it is fake snow that has been haphazardly blown across the street, and on vehicles, and various structures. If you look at buildings in the background of most shots, there is no snow or icicles present on the rooftops.

Lack of motion blur during the car chase on the El reveals that it was filmed with the vehicles moving slowly and then sped up to give the appearance of a chase.

When chasing Gonzales, Ray and Danny first drive on commuter railroad tracks. When they enter the tunnel, they are suddenly on an El line even though there is no apparent third rail. The third rail appears as they exit the tunnel.

During the chase through Chicago, Ray Hughes is moving his hand on the steering wheel but the wheel itself does not move.

Patti LaBelle's name is misspelled ("Pattie") in the closing credits.

The cast list in the closing credits misspells "subpoena," "tattoo" and "Colombian" and mistakenly omits the "s" in "Customs Official."

As they're sitting in the taxi, just prior to it being picked up by the garbage truck, Billy Crystal is reading his lines but flubs them. When he says 'We've given our best years to the city, nobody gives a damn,' he is meant to say 'nobody gives a damn if we stay or leave.' instead he starts a new sentence with 'If we stay or leave,' realised his mistake and ad libs: 'If, if we stay or leave, doesn't matter, if we live or die, doesn't matter..'

When Ray and Danny are driving around in Julio's BMW, they stop by the playground to shoot hoops with the same hostile group of guys they played against in the beginning. However, in the wide shot, when Ray makes his basket, one of the extras in the supposedly hostile group raises his arms in triumph celebrating the basket.

When Ray jumps down from the top of the garbage truck after shooting through its windshield from above, we clearly hear the sound of his gun hitting the ground, but when he pops back up to approach the truck from the front, the gun is in his hand.

When the limo carrying Gonzalez is hit by the El and flipped upside down, the two cylindrical housings for the pyrotechnic effects are clearly visible on the belly of the car.

When on the red scooters in Key West, Danny and Ray are driving in the wrong direction as they pass Key West by the Sea condominiums on South Roosevelt Blvd.

The female that gave Ray his birthday cake at the bar back in Chicago is one of the same two girls in bikinis that was on the boat with him and Danny in Key west while they were fishing..

Billy Crystal playing an Italian? That just does not fly, bubbeleh.