Look out! A huge tarantula!
It's hard to believe, but there was never a tarantula of any size in this desert. The breathlessly realistic effect was created with an advanced film overlay technique. First, a tarantula was filmed against a white background in a controlled environment. That footage was then exposed over top of a static shot of the desert. The explosion at the end employs the same process. When properly executed, it's completely indistinguishable from reality.
The House on Haunted Hill (1959)
This shockingly realistic skeleton was actually controlled from above via a network of near-invisible strings. This allowed the skeleton to move both its body and arms without anyone in the audience suspecting they were seeing the work of a puppetteer. Amazing!
Forbidden Planet (1956)
The robot is a guy in a robot suit. It's not really that impressive, but people keep asking so we threw it in here.
The Incredible Shrinking Man (1957)
Are you ready to have your mind blown? This cat and this man were never in the same room at the same time!!! Any frames containing both the man and the cat were achieved through matte composite.
It Came From Beneath The Sea (1955)
Effects wizard Ray Harryhausen created this tentacle attack by using stop-motion models, rear-projected onto live footage of San Francisco. The result is the most realistic recreation of a major metropolitan octopus attack we have yet produced.