Continuity mistake: Major Kang Min-gil in the opening meeting stands up and mentions the meeting when both North and South Korea agreed to build a nuke. The female scientist in the wide shot is leaning with her chin on the back of her hand in the wide angle, but at the mid-sentence cut she has the palm of her hand along her cheek. (00:04:35)
Plot hole: If the creatures are strong enough to simply burst through the walls, as shown at the end of the film, then the creature upstairs should not have been stopped by the small door that Bozo, the bartender and heroine shut on it to stop it. It was one of the larger creatures as well, so it could have easily gotten through.
Other mistake: After the Joker has become a vampire, you can still see his reflection in metal poles and such while he is chasing Batman in the bloodbank. (00:47:00 - 00:49:00)