Goofs

(at around 40 mins) Harry is filling a large (~30 CC) syringe in an attempt to kill his wife; later, when he and the nurse are shocked to see she has become a giant, he is only holding a small (~ 1 CC) syringe.

The station wagon that the 30-foot giant picks up is a 1958 Plymouth. The car that lands on the ground is an early 1950s Chevrolet. When it cuts back to the car, it's a 1958 Plymouth.

Although the alien is a giant, when the sheriff and Jess go into the "satellite" (the alien spacecraft), the on-board equipment, passageways, and interiors are for human-sized inhabitants.

At one point during the fight between Harry and Jess, Jess hits Harry on the left side of his face, but when Harry falls over the chair, he holds the right side.

As Nancy picks up Harry, the dummy standing in for him is off-scale, looking larger than the real Harry does on the prop giant hand.

When Nancy slams on the brakes at the beginning of the movie, the tires make a screech sound, but it's clearly a dirt road.

The Sherrif says 'it'll be dark in a half-hour'. The shadows show it's not far away from Noon.

How Nancy can be fifty (or thirty) feet tall yet remain in a standard-size room is never explained.

When the alien ship lands on the road in front of Mrs. Archer, the strings holding it up can be seen.

The giant alien and Nancy Archer as a giant go from transparent in the long shots to solid in the close-ups.

When the 30-foot giant grabs the car, the entire frame of scene behind it follows as well.

Some shots of the giant alien in the desert were not matted; instead, the negatives were simply superimposed so that dark portions of the alien are almost transparent with the background showing through.

The title may say "50 Foot", but at no point in the movie does anyone say that. In the movie, it's said the giants are "30 foot".

When it is discovered that Nancy has grown to gigantic proportions, everyone who enters her bedroom simply stares at her hand.

When the giant Nancy walks up to Tony's Bar & Grill, a crew member can be seen in the rear-view mirror of the car the two teens run out of.

In the wide shot as Nancy and Harry are confronted by the giant alien, a lone figure can be seen crossing a field in the background.

In the first scene, a newscaster describes sightings of a strange object over the Barents Sea; Cairo, Egypt; Capetown, South Africa; and Auckland, New Zealand. He then walks over to a globe to show the flight pattern and points out the locations on it: Barents Sea, Cairo, Auckland (clearly pointing to South Africa), and then New Zealand.

When Nancy is normal-sized, she is a brunette with a short, styled hairdo. When she's super-sized, she's a blonde with long, curly hair.

When the nurse calls the sheriff's office to report that Nancy has escaped, Deputy Charlie writes the details down with his left hand. But as he runs out of the office his gun and holster are on his right hand side. A left handed person would holster a weapon on the left side.