The Phantom Planet

In this 1961 black and white film, earth spaceships are disappearing, apparently colliding into a mysterious planet that seems to vanish and re-appear on a moment's notice. Another ship is sent to investigate, but it is thrown off course by a meteor storm which damages the spacecraft. The two astronauts are forced to perform an EVA to repair their ship. The EVA doesn't go well -- one astronaut is lost, while the other crashes into the phantom planet.
The planet's humanoid inhabitants are only six inches tall, and exposure to the planet's atmosphere causes the astronaut to shrink to their size. They plan to keep the astronaut for some nefarious purpose that I'll bet probably involves some sort of mating ritual. And yes, it looks like I'm right -- the alien's leader has offered the astronaut two women to chose from, one who happens to be mute. As the earth continues to investigate his disappearance, the astronaut chooses the mute women. He begins to work out a plan to return to earth, when some other evil aliens attack -- eep! (You can tell that they are evil because they look like monsters!) An evil alien captures the mute women -- again with the mating! Our hero is forced to fight to the death with a man in a bad costume! (And that man is Richard Kiel, who has had a long career in tv and films, and is most famous for playing the giant hired killer Jaws in two James Bond films.)
Then when the earth astronaut saves the mute women, it turns out that she can talk after all. She tells him that he loves her, so naturally he returns to earth without her.
The film is very talky and contains almost as much technobabble as a bad episode of Star Trek: The Next Generation. But let'd give them some credit, they are trying to give some scientific explanation for the aliens' advanced force-fields and weapons which is something that most sf films tend to ignore.
The effects are surprisingly good and effective on occasion considering the obvious lack of budget, but the evil alien costumes are pretty goofy. The pacing is slow -- no question -- but on the other hand, late at night after too much Diet Coke and pizza when you can't sleep, you'd probably find yourself being entertained if you stumbled on this while channel surfing.
It ain't all bad.
One wonders if George Lucas ever saw this movie and named Star Wars Ep. I: The Phantom Menace as a nod to it.