The poster artists were purportedly not shown the puppet nor any other artwork from the film's production and concluded that the monster was a giant eagle or hawk. Thus, the creature in the posters looks nothing like the beast in the film.
In an interview, star Jeff Morrow said that neither he nor anyone on the film saw the title "monster" until they went to the film's premiere in Morrow's home town. It turned out that producer Sam Katzman had contracted with a low-budget model-maker in Mexico City to construct the "Giant Claw" and no one in the cast or crew had any idea it would come out looking as bizarre and, frankly, laughable as it did. Morrow said that the audience roared with laughter every time the "monster" made an appearance, and he wound up slinking in embarrassment out of the theater before the film was over so that no one who knew him would recognize him.
The footage of a B-25 taking off to attack the giant claw was taken from the movie "30 Seconds over Tokyo" You can clearly see the crew artwork belonging to Van Johnson's plane, "The Ruptured Duck", on the side of the nose.