Best animated movie mistakes of 2015
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.
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."
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: In order for Superman, Wonder Woman and Batman to break into the secret room, they knock it down. Four enemies who were waiting for them in front of the door are crushed by the falling door and blood is splattered, forming a pool of blood in front of the door. During the fight that follows, there are several shots where the knocked over door is shown, but the pool of blood at the front of the door has vanished.