Continuity mistake: When first arriving on Earth the aliens do a clean up of things not needed, one of these being toilets, then in a scene minutes later you see the main alien character brushing his teeth with a toilet brush standing next to a toilet. (00:05:45 - 00:07:00)
Other mistake: Two cars with the same license plate numbers are seen as the minions are hitch hiking on the road. The plates of the hippie wagon and the old lady's car both read D-6413.
Plot hole: Joy and Sadness are stuck outside of the control center. They are trying to figure out how to get back, and encounter maintenance workers who are discarding old memories. The maintenance workers show that they have the power to send memories back up to the control center to be played. Why couldn't they send the core memories that Joy had back up the same way? Better yet, why not use that method to send Joy and Sadness back up to the control center? The director of the film is even aware of the plot hole, and said "Yeah, well then we wouldn't have a third act," before explaining how the idea of recalling memories was added in later, "box[ing] [the screenwriters] in a corner a little bit."
Factual error: The main character from the video game "Paperboy" is among the alien invaders in the final battle; since that game was first released in 1984, he shouldn't be there, because the probe the aliens received featuring video game footage was launched into space in 1982.
Continuity mistake: When SpongeBob says he should sacrifice himself, the squidosaurs Rex has Mr. Krabs in his hands, but when SpongeBob walks to the counter, Mr. Krabs is right next to Squidward. When the camera zooms in on a group of citizens and Squidward, Mr. Krabs is gone. Then, another shot of the squidosaurs Rex, Mr. Krabs is in his hands again.
Plot hole: In the beginning, vampires are shown to be invisible in photos but then they seem to appear in videos like security footage and social media posts.
Continuity mistake: Charlie Brown is using a pen to write a book report. The black ink leaks and gets all over his hands. When he walks to his dresser to get a pencil, all the ink stains are gone.
Suggested correction: He wipes the ink on his shirt.
Continuity mistake: Spot finds four other humanlike creatures and goes to them. Arlo is standing several feet in front of them. He begins to push some dirt by using his nose. A close-up then shows him using his nose to draw a circle around the five others but he is standing much too far away to be able to do this.
Continuity mistake: When Shaggy and Scooby are approaching the Demon as he eats, it is shown that he is eating from a platter of hamburgers and french fries. Scooby and Shaggy bump into his table, knocking the food all on the floor. When Shaggy and Scooby quickly put all of the food back on the table, it now has french fries and hot dogs.
Other mistake: When Marry Anne flies into the dark forest for the first time she drops the boutonniere. After seeing the primrose petal she flies off empty handed but has the boutonniere later when she meets Roland.
Continuity mistake: Once Superman, Wonder Woman and Batman break into the secret room in the bunker, they begin fighting with the enemies inside. The enemy with the leopard claws scratches Wonder Woman's back, leaving a long claw mark along her back. Just over a minute later, after Trevor arrives, the claw mark has vanished. (00:07:25 - 00:08:40)
Continuity mistake: Lotte is in her room looking at the checklist for the parade. The size and angle of the quill pen change every time there's a cut. (00:14:40)
Continuity mistake: After Thomas biffs the trucks, the position of the way they are derailed changes between shots.