The Thing from Another World (1951)
Despite the tagline's claims, "It" doesn't creep or crawl and actually gives fair warning by walking kind of slowly. Considered a sci fi/horror classic, but definitely cheesy enough to be a great riff. The characters often don't seem to realize that they're supposed to be in the arctic. I'm a huge fan of this original and of the 1982 remake.
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Kamikaze-Kumquat commented
I mean, come on, it's a space carrot!