Kelso opens his bottle of Coca-Cola by slamming the cap against the frame of the cockpit bubble, breaking the neck completely off, but when he drains the entire bottle into his mouth (after a quick cut), the bottle neck is intact.
When Captain Birkhead and Donna get out of the car, Donna is handcuffed to an MP. Their handcuffs disappear a few minutes later, when the house collapses.
In the theatrical trailer John Belushi's character is named "Wild Wayne Kelso." In the movie, his name is "Wild Bill Kelso."
Ward loads a 4 round clip in the 40 mm anti aircraft gun. He then fires one round. Yet, before firing again, he loads another 4 round clip.
The "stop light" threat condition signal in the air defense coordination center is shown twice. The first time, when the trainer is incorrectly reported as enemy aircraft over the reservoir, it switches from green to yellow on the appropriate dialogue command. A few minutes later, a decision is made to "go to red," and the signal moves from green to red. It should have been yellow.
The P-40 John Belushi's character flies is called a "Tomahawk" in the film. P-40's flown by US forces in WWII were called "Warhawks". P-40's flown by British and Soviet forces were called "Tomahawks".
A submarine is a big chunk of steel and uses more thousand Ampere electric cables, so it is highly unlikely a miniature toy compass will head to true North onboard.
The P-40 flown by "Wild Bill" Kelso would not have had the shark tooth paint job on the plane. This was only used by the Flying Tigers in China and would not have been used on a plane stationed in the United States.
Kelso Identifies himself to Maddox as "Captain Wild Bill Kelso, United States Army Air Corps". The US Army Air Corps was changed to The US Army Air Forces on June 20, 1941, about 6 months before the time setting of the film.
"Wild Bill" Kelso's leather jacket has patches on the right front pocket indicating that he has shot down three German and three Japanese planes. Given that the war had only been declared a few days before the time when the movie was set, it would not have been possible for him to go into combat against both the Germans and the Japanese in that period of time.
Herbie and Claude change position on the ferris wheel. Spielberg did that deliberately for comedic effect.
The front door of Ward Douglas' house is totally intact while it slides downhill. But in several scenes, the front door was broken several times.
After Kelso crashes his plane, he opens his parachute. The wire pulling the chute away from him is visible.
When Wally is dancing on the table, the real dancer's feet jump up as Wally jumps down.
When Angelo pushes the anti-aircraft gun back towards the house with his car, he never puts the car into gear.
In the scenes over the Grand Canyon, the aircraft banks to avoid hitting a canyon wall, yet the cockpit shots show the aircraft flying straight and level.
The tank crew has an African-American member. The US Army wasn't officially desegregated until 1948. Limited desegregation came to combat units in December 1944 and January 1945, during the Battle of the Bulge.
In the USO dance scenes, it's clear that many of the women, including Betty (Dianne Kay) and Maxine (Wendie Jo Sperber) are wearing pantyhose instead of thigh-high stockings. Pantyhose were not invented until the late 1950's and not made commercially available until 1959. This is especially noticeable whenever women's skirts fly up. At one point, Corporal "Stretch" Sitarski (Treat Williams) lifts Maxine up and drops her down onto a table. When he does, her skirt flies up and the dark panty portion of the hose can be seen.
When Ned Beatty crashes the cannon into the house, to get a better shot at the Japanese submarine, Bing Crosby can be heard singing, "I'll be Home for Christmas", which was recorded October 4, 1943.
In the USO scene, Wendie Jo Sperber's character is wearing pantyhose, which were invented in 1959.
During the general's speech at the airport, a number of WW2-era planes serve as a backdrop. Some new airliners and what seems to be a B-52 are visible in the background.
As General Stilwell is watching Dumbo (1941), he says, "Get out of the way. I can't see the screen." However, he can be seen saying something else instead of "screen," possibly "show."
When Donna says "You get me up in that plane, then we'll talk about forward thrust," the reflection of her mouth movements in her hand-held makeup mirror don't match her voice.
The wire guiding the torpedo can be seen.
The camera crane is reflected in Stilwell's glasses.
The reconstruction of Hollywood Boulevard has some buildings in the wrong place.
The caption in the opening scene says it is supposed to be Northern California; however, the scenery is of Cannon Beach in Oregon at least 400 miles away.
The sub shoots down the ferris wheel, it rolls down the peer, goes over the edge, and sinks pretty much in an upright position. It seems highly unlikely that the water would be deep enough for it to do so. Later, the tank falls in the water at roughly the same position, yet its turret remains above the water line. Obviously the tank isn't as tall as the ferris wheel.
Herbie Kazlminsky says that objects fall at 32 feet per second. This should be 32 feet per second per second.
Capt. Wolfgang von Kleinschmidt speaks German thoughout the film. Unless everybody on the sub speaks German too, he should be speaking Japanese.