When Duke is in the Mint bar, his cigarette is broken when he lights it. While he is smoking it, the broken part falls off. He spins around in his stool looking for his attorney, the broken part is there again.
When Dr.Gonzo hits reverse to pick up the hitchhiker, Duke is thrown backwards.
When Duke and Gonzo drive into Las Vegas to the Mint Hotel there is a banner which reads: '$100,000 Mint 400'. However, at the actual race a banner reads: '$50, 000 Mint 400', which can also be heard by the announcer at the race.
In the first hotel room, Duke is crouching behind the bar when the photographer comes in. The ice bucket on the tray disappears between shots.
When Duke spots the patrolman behind him, the pattern on the center line on the road in front of the car is different from that behind.
In The Flamingo Hotel Rauol Duke looks in the peephole to check on Lucy. There's no way Duke can clearly see her. Peepholes can only be clearly seen looking from the inside (of the room) outwards (toward the wall and hallway).
The film is set in 1971. The Ford Maverick was first introduced as a 1970 model. Even in the hands of Raoul, there's no way a car less than two years old would be that rusted and weather beaten. Dented and smashed, of course, but that kind of paint damage takes a decade or more.
The California Highway Patrol officer says that the town of Baker, California is outside of his jurisdiction. Although CHP officers are assigned to a specific office, technically the entire state is his jurisdiction.
David Brisbin's last name in the closing credits is misspelled as "Brishin."
While driving down the Vegas strip in the convertible on the way to the Debbie Reynolds concert, they pass Binion's Horseshoe Hotel and Casino twice. However, the scenes outside of the car are not meant to be realistic. It shows lots of casinos that are not in order, but this is from the mind of a drugged out driver - the car itself is floating in air the whole time.
In the last scene of Duke sitting in the trashed hotel room, the camera moves across the liquid-covered floor towards him, and clearly tips over a candlestick on the left of the shot.
After Dr. Gonzo takes over driving through the desert in the red convertible during the opening scene, the gear shift for the automatic transmission is all the way up, indicating it to be in PARK.
In a few shots taking place in the Chevy's interior, you can see the car has white vinyl door panels from a 1973 or 74 Impala (or Caprice convertible), while the main "Red Shark" is actually a 1971 Impala convertible. The Impala had slightly different door panels for 71/72 than the 73/74, but was essentially the same car overall. Apparently another car was fixed up for use in the movie as a backup or secondary vehicle and used for some shots from the inside.
When they are stopping on the highway because of the bird-like hallucinations they stop on the side of the road. They soon speed up after that and the wheels make a screeching sound. Tires don't screech on dirt because there's not enough friction.
When Duke and Dr. Gonzo sniff the ether, Duke throws out his lit cigarette. A moment later, he has the ether soaked flag to his face and a new lit cigarette in his hand. For a drug connoisseur like Duke, it's highly doubtful he'd be smoking around ether fumes, especially since he had just earlier thrown out his cigarette to sniff.
Dr. Gonzo spoofs the "Richard Nixon salute" when he gets on the plane at the end of the movie. Nixon didn't resign or do the classic "salute" until 1974.
As they drive through Vegas at night, a marquee sign in front of The Plaza advertises a steak and lobster dinner for $11.99 - more of a 1997 than a 1971 price.
When Duke is in his hotel room near the end of the movie, the camera pans across the television quickly, showing footage of an M1 Abrams tank. The film is set in 1971, but the first Abrams was not built until 1978.
When Duke is talking to Dr. Gonzo from the phone-booth in the desert, a Dead Kennedys' DK logo is seen spray-painted on the door of the booth. The DK logo wasn't yet in existence in 1972.
The California Highway Patrol squad car used to chase Duke was a 1974 Plymouth Satellite. The real California Highway Patrol used Dodge Polaras at the time. Additionally, the Federal Signal Corporation "AeroDynic" red and blue light bar on the roof of the police car was not invented until the 1980s and would not have existed in 1971.
When Duke is trying to calm Gonzo down with the mace, Dr. Gonzo screams and whines, but his mouth is closed
When Duke and Gonzo are stopped with the hitchhiker and Gonzo grasps the hitchhiker and says, "The truth..."
When Duke is in the desert, talking on the payphone at the junk yard, on one of the crane shot swoops, the footage was edited in reverse. Notice the smoke going back down into the smoking car, as well as the papers on the side of the phone booth moving quite rapidly.
When Duke is pulled over on the side with the patrolman (Gary Busey) and is outside of the car, you can see the radio microphone cable on the ground right behind Duke's car.
White SUV visible in opening scene: in the opening convertible scene, just after picking up the hitchhiker and around the point where Duke narrates "...when my attorney starts screaming about bats..." in the closeup shot of the hitchhiker. Just before the shot changes, an out-of-place white SUV can be spotted the far right of the screen behind the hitchhiker, parked along the desert highway.
During the low-angle tracking shot along the water in the floor in the Flamingo Hotel room, the camera clearly knocks over a syringe and pushes it across the water.
After they pick up the hitchhiker in the desert Duke hits Gonzo on the neck from the back seat. After Gonzo regains control of the car the wind is blowing his shirt open, revealing a cable for his microphone.
Shadow of camera visible when Duke calls Gonzo near Baker.
At the end of the movie, Raoul Duke is driving from Vegas to Los Angeles, when a sign reads "Los Angeles, 400 miles". In actually, at best Los Angeles is only 270 miles away.
In the beginning of the movie, it is implied that they are near Barstow, CA, which is in the Mojave Desert. However, the area they are driving through has saguaro cacti, which do not grow anywhere in the Mojave Desert.
When Dr. Gonzo is walking towards the payphone, the mic and boom are reflected in the window.
After Duke has received the phone from the dwarf at the hotel, he looks up while speaking into the phone and the boom mic is reflected in his sunglasses.
When Duke is going through his drug and liquor collection at the beginning of the film, he points to his bottle of tequila. However, that bottle is clearly labelled "Wild Turkey."
In the North Star Cafe, when Dr. Gonzo counts out money for the pie, he stops at five, but he actually flips down six bills.
When asking the question about Margaret Mead, the cop at Dr. Bumquist's lecture addresses him as "Dr. Bloomquist", which is his name in the novel.