Revealing mistake: When Sonic and Tails arrive in Green Hills on the biplane, Tom and Maddie are looking up at them, but not focused on the same point. Instead, Maddie is looking to the left, and Tom to the right.
Revealing mistake: This happens in the second ceremony when Wolf didn't press the button to shut off the lights to steal the golden dolphin because of the good comments. Few seconds later, the lights shut off, and you can see that the meteor on the top disappears at the time.
Revealing mistake: The guy with the sunglasses changes from behind and in front of shots. (00:09:46 - 00:10:15)
Revealing mistake: It was quite obvious that the beaver was fake, and not a very good one relative to the capabilities of contemporary CGI. (The first time, the beaver was presented as real; the second time, it was meant to be comical). (00:59:20 - 01:29:13)
Revealing mistake: The owl that JP saw was obviously "fake" (stuffed or CGI). Its nose was crooked and its puffy cheeks made it look like it had cheek filler injections; owls have flat faces. (00:32:50)
Revealing mistake: Dave Bautista announces that he has arrived. There's a close-up of the kickstand, and you can actually see scratches on the asphalt from previous takes (spotted also by Rian Johnson himself in his video breakdown of the arrival scene for the Vanity Fair youtube channel). (00:15:10)
Revealing mistake: The very first shot of the movie, supposedly of Anya Taylor-Joy lighting a cigarette, does not match the following shot on the pier; the cigarette appears to be black and with a brand sleeve instead of the normal one she is smoking. The background confusingly looks more like an interior than the pier she is standing on, and the lighter is a common Bic-style one instead of the Zippo she is using also later in the movie. That's because it's actually stock footage. You can literally find the clip yourself on Shutterstock and similar websites, by the description "Close-up of the silhouette of a woman's face sticking a cigarette into her lips, igniting her with a lighter, and exhaling smoke. The grim concept of the harm of smoking in a low key." (00:01:00)
Revealing mistake: The "snow" that Kip and his friends jumped into after leaving the bath house was obviously fake (like the "snow" on the pine trees). Beads of "snow" do not fly into the air when impacted by a weighted object, such as a body. (00:22:32)
Revealing mistake: When Otto, Tommy and Marisol find the frozen cat outside of the house it is a puppet prop. A few seconds later Tommy is holding it now back to a real animal and is bone dry.
Revealing mistake: A white truck could be seen in Tamra's rear window, following her car at varying distances. After Tamra hit Randall on his bike, the white truck was still there but gone when the camera returned to a front view of Tamra. Use of a green screen - the truck could not have gone past the accident or "disappeared." (00:03:35 - 00:04:10)
Revealing mistake: The front view of the pirates in the golf cart with Darcy and Tom does not show the driver turning the steering wheel at all, which would mean the road was straight, but the when the road becomes visible again, it is diagonally behind the golf cart. (00:36:45)
Revealing mistake: The stairs are a prop. About a dozen steep steps - just to the landing - are almost as high as the front door. (00:55:48)
Revealing mistake: A dog would not be able to jump through a vehicle's window and land on shattered glass covering the rear seat without getting its paw pads cut. The shattered "glass" that Lulu was standing and sliding on appeared to be ice. (01:07:29)
Revealing mistake: While with Abigail, doors open to reveal a city and a plane behind which rises big jets of air that move Loretta's hair. However, the decorations on the table don't move a single inch (until several shots later), giving away that the city behind is CGI.