Revealing mistake: When Rufio brings the sword down on the rope holding the slingshot, you can hear the intended sound effect, but the rope is not cut. (01:05:20)
Revealing mistake: When Robin crashes through the stained glass window to save Marian and fight the sheriff, the panes of glass flutter in the breeze, revealing it to be fake glass.
Revealing mistake: In the junkyard, Leo and Raph grab a long pole and plough through several Foot Ninjas with it. It is painfully obvious the ninjas react to the pole before it ever hits them. Especially the guy on the ground. (00:53:20)
Revealing mistake: Gratuitous car explosions are nothing new in action films ... but this time the ambulance explodes in mid-air before even hitting anything. (00:32:22)
Revealing mistake: During the night surfing scene notice that the sun is evident in the background (look closely it does not appear long). There are also shots where you can see clouds and faint blue sky. Moments later you see Keanu and Lori sitting in the water with completely different lighting which was actually taken at night and further distinguishes that the surfing shots were not actually done at night time. I heard the scene was shot during the day with a filter so it looked like it was shot at night.
Revealing mistake: When the king's youngest daughter mounts the Polar Bear King the lack of effort reveals that she does this with the help of a cunningly placed stepladder. (00:25:35)
Revealing mistake: When Jack is being chased by the bear, at one point you can see a piece of food thrown into the shot to make the bear turn around.
Revealing mistake: When Bill and Ted, are playing Battleship, with Death, you can see at the bottom of Death's neck where the crease is of the cap that is covering the actors head to make it look bald.
Revealing mistake: Thelma and Louise in one scene are driving at a very high speed with Brad Pitt in the backseat wearing a cowboy hat that never flies off, much less even moves with the wind.
Revealing mistake: During the dinner, Dennis is addressing his sister. As she comes over by him, look at his left sleeve. It appears to be matted in, as it has a definite line at the edge of the fabric, where all other edges are softer. Then as Eldona sits the plate down, you can see a flutter between the images of Dennis' arm and the plate. Then, as Eldona turns around, you can see her dress through the gap between Dennis' arm and the plate. (00:36:30)
Revealing mistake: In the first shot of the club scene, where we see the clarinet up close, the ligature (the metal band that holds the reed in place) has been placed upside down. This would make it extremely difficult, if not, impossible for the clarinet to play a single note. So, the "clarinet player" physically could not play his instrument, even if he wanted to. (00:51:00)