Continuity mistake: Just before the giant tarantula attacks the house where heroine Mara Corday is studying, you can see several book on the library table at the big picture window. The largest book on the table keeps shifting positions in several scenes.
Continuity mistake: Lobo has a very distinct scar on his cheek in the beginning and end of the movie. However, just after Dr. Strowski has entered the house, Lobo is seen coming down the stairs, and his scar is completely gone.
Character mistake: After Cal goes to the secret lab in Georgia, he and two others go into his new lab. When they enter a cat jumps up on the counter. Dr. Adams says "This is Neutron. We named him that because he's so positive." Neutrons are neutral and electrons are negative. It's protons that are positive. They should have named the cat Proton.
Revealing mistake: Air can be seen coming out of the creature's head at one point in one of the tank scenes.
Other mistake: While all the business signs in downtown Osaka are properly in Japanese, the local newspaper, The Osaka Times, is printed entirely in English.