Continuity mistake: When Oskar intercepts Lacke's plan to kill Eli in the bathtub, Eli kills Lacke and drinks some of his blood, leaving some blood on her lips. She then kisses Oskar, which in turn leaves some blood on his lips. In the cut right after that the blood is gone from his lips. Later on it appears again, when he tastes it with his tongue.
Continuity mistake: When Eli runs out of the basement and then runs outside, after she scares Oskar by licking his blood off the floor, there is snow everywhere. She then climbs up a tree, and when she is at the top of the tree there is no snow anywhere to be seen in the background. From the following day on the snow is back.