Factual error: [Special Edition] The Statue of Liberty is incorrectly shown to be facing the Narrows bridge.
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: 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. (01:16:42)
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: An animal that lives in the deep sea cannot live in the open air above the water.
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: When Kirk falls off El Capitan, he is shown falling all the way past the tops of the trees. I have been to Yosemite and the trees are tall, but not tall enough to give Spock enough time to slow then stop Kirk's fall.
By the time Kirk reaches the top of the trees, he is traveling at terminal velocity (assuming Kirk was halfway up, about 2000 feet from the ground, and an initial fall rate of 32 feet per second, per second), approximately 120 mph, about 200 feet per second. If the trees were 1000 feet tall and Spock caught Kirk right at the top of the trees, that would give him 5 seconds to slow down and stop Kirk. Impossible. Fortunately, in the movie he was able to accomplish this feat, or it would have been a very short movie. :).