Continuity mistake: Aquaman coughs up blood after he is stabbed by Wonder Woman. Some blood goes on his chin. Throughout the rest of this scene, the blood on his chin keeps going from the right side to the left side of his chin. (01:10:25)
Revealing mistake: As Elsa sings "Let It Go" she pulls her hair into a long braid going down her back. She pulls it with her left hand from behind her to in front, but the end doesn't flip over her shoulder, she just pulls it straight through to the other side without going over the top. (00:34:10)
Other mistake: Wolverine shields Yashida from the blast, burning off all his hair. Somehow his pants manage to remain unaffected by this, as seen later when they are climbing from the pit.
Continuity mistake: In the scene where Thor tells Jane to hold on, she's on Thor's right side and Mjölnir (the hammer) is in his left hand. As they are traveling through the Bifröst to Asgard, the position of each has changed. (00:28:20)
Continuity mistake: After Oz tells Finley he'll get a nice big pile of bananas, Finley tosses down Oz's bag and goes on a rant about monkey stereotypes. When he first throws down the bag, he is close to the middle of the yellow brick road. It cuts to a close up and he is suddenly standing right next to the edge of the road. (00:46:25)