Factual error: George comes up with the idea to raise money via a public share issue in Channel 62 around mid-morning, and promptly announces the telethon on the air and by midnight of the same day they have the money they need. One problem. Even if George had access to a compliant attorney and Channel 62 was already a company authorised to issue shares, a public issue would take at least ten days to organise. There are all sorts of notice periods and filing dates to which the share issuer must adhere. I know - I've done it.
Factual error: When Bill and Ted grab Beethoven, we are shown the piano he was playing which is a Steinweg (Steinweg later changed his name to Steinway when he immigrated to the United States). Steinweg made their first piano in 1835, and the model shown was built in Braunschweig so must have been made after 1858, but Beethoven died in 1827, years before a Steinweg piano existed. Also the onscreen graphic says it's 1810. (00:47:50)
Factual error: When Harry and Sally are driving away from the University of Chicago at the start of their road trip there is a long shot of them driving on Lake Shore Drive, but they are heading south towards the city with the lake on their left. If they were leaving the city from UofC, which is in Hyde Park, they would already be driving away from the city on Lake Shore Drive.
Factual error: Hooch is a french mastiff. The dog he gets pregnant is a collie. Different breed dogs do not make purebred puppies. Hooch's pups would be part collie, part mastiff. In the end of the movie, one pup is pure mastiff like hooch and 4 are pure collies like their mother.
Factual error: In the beginning sequence where they show the sperm first fertilizing the egg, it is biologically incorrect - only the head part of the sperm enters an egg, everything else stays on the outside and eventually dies off.
Factual error: When they are at the Cadillac dealership, taking delivery on a car in 1956, the American flag in the background is incorrect. It should have been a 48 star flag, not a 50 star flag.
Factual error: While Fletch is riding with the bikers, they stop at a stop sign where a family in a station wagon roll up their windows in fear. A sign at a service center in the background is the Castaic Junction, which is in the greater Los Angeles area. The movie is supposed to be taking place in Louisiana. (01:12:35)
Factual error: When he bats, Jake uses a helmet with no earflap. In 1983, it was instituted that players must wear a helmet with at least one flap; however, it's possible that Jake is exempt from this rule under Major League Baseball's "grandfather clause," which allows any player who played before 1983 to continue using the flapless helmet. (01:34:40)
Factual error: When Harry is standing on the ceiling fan, the young boy pulls the lever backwards to increase the speed. If you read the side of the lever, you can see that the boy is actually pulling the lever to the slow direction. (00:40:30)
Factual error: Marty is pursuing Biff at the high school as the other Marty pulls up with Lorraine in Doc's car. In the parking lot, the car closest to Biff is a brown 1957 Chevrolet. The front grill and styling are distinct and unique to the 1957 model year. In November 1955, it would be plausible to see a 56 Chevy in the lot, but a '57 is a bit early.
Factual error: As Toxie is removing the guy's intestines with his bare hands, you'll notice that there's absolutely no blood on the intestines.
Factual error: In the opening scene at the baseball game, the announcer thanks the crowd for coming to see the St. Louis Cardinals. The fans are sitting in yellow seats, but all of the seats in Busch Stadium in St. Louis are red.
Factual error: In the lunch scene outside their office, Larry and Richard are at the food stand and notice Bernie walking into a building. The entrance awning reads "East 70th Street". As they walk away the street sign behind them reads "52nd Street". Apparently they must have superhuman vision which allows them to see 18 blocks away.
Factual error: After their parents give up looking for the kids, there's a "time passing" scene showing the lit attic window from the outside of the house, in which the night grows lighter until it's morning of the next day. But the moon in the picture doesn't move. How can the moon stand still if time is passing?
Factual error: The girls need to pay $7.50 for 36 badges. However, badges are usually paid for by the leader out of the weekly dues money, and at $10 a week, and not needing to pay for a weekend meeting place (they seem to meet at her house most of the time), they should have plenty of money to pay for them.