Continuity mistake: Rumplestiltskin looks completely different in this movie than he did in the previous film Shrek The Third; Prince Charming momentarily talks to Rumplestiltskin in the tavern during the third film, and the character looks completely different, has a different voice and different demeanor.
Continuity mistake: During Andy's daydream at the beginning of the film, Mr. Potato Head has an eye patch over his left eye. When the daydream cuts back to reality we see that Andy has removed Mr. Potato Head's left eye to symbolize the eye patch. But when Andy's mum comes in with the video camera, his left eye is suddenly back in. (00:01:15 - 00:05:25)
Plot hole: When Astrid gets on Toothless for the first time, Toothless takes off uncontrollably and tries to scare her. Hiccup seems to have no control over him at this time. How is that so if with the new tail fin, Toothless cannot fly without Hiccup's precise control of the tail fin? That whole sequence would have fallen apart. This mistake was even admitted to on the DVD commentary. (00:53:35)
Continuity mistake: Just before Flynn cuts off Rapunzel's hair, there is a shot from behind him and he reaches up with his right hand to push her hair behind her ear. His arm is visible up to his forearm and the shackle is nowhere in sight. However, in the next, wide shot, the shackle is suddenly up around his wrist. (01:01:20)
Continuity mistake: While Megamind is in the Metroman Museum, he uses his dehydrator gun and turns Bernard into a little blue cube. He puts the cube in his pocket, then picks up Bernard's cellphone and glasses. At the end of the movie, inserted into the credits is a short scene where Minion is doing laundry. As he approaches the washing machine, Bernard pops out of it, having been rehydrated in the wash - with his glasses perched askew on his head. (00:30:05 - 01:28:20)
Continuity mistake: In the second scene where we first meet ranger Smith he is shuffling with some information pamphlets. When Ranger Jones yells his name he is startled and drops some of the pamphlets, but we can see that the last ones he put in were on their side. When the camera changes shots there appears to be some pamphlets sticking out. Then in the next shot they are gone. The pamphlets change locations between shots.
Continuity mistake: During the last fight with Darkseid, there's changes to what the farm looks like. At one point, instead of the windmill there's a building, which we never saw when Clark drove past the spot. And the overturned truck is missing in a several of scenes even though it should be visible.
Continuity mistake: In the final battle scene after the Band reaches the canyons and are on a cliff overlooking the Guardians, you can obviously see that Twilight doesn't have his lute. After focusing on Soren struggling to remove the pot of tar, we see Twilight flying with Digger and Gylfie, but with his lute. Impossible to be so fast. (01:11:55)
Audio problem: When Niko is going to get the key for somewhere for Zoe to hide and then Zoe disappears he says "Zoe"? When he says it his mouth does not move but once he finishes saying it that's when his mouth moves.