Teenagers From Outer Space(1959)
A group of aliens land on Earth and intend to use it as a herding ground for their major food source the gargons (lobsters). However one of their party, Derek decides to not to go through with the plan due that there is intelligent life on the Earth. The others laugh at him and continue to go through their plans. Derek escapes and meets with Betty Morgan and her grandfather, he continues to learn the ways of Earth and it drives him to protect the planet. However one of his fellow crewmen, Thor, is order the retrieve the rebellious alien, dead or alive.
The film appeared of the show Mystery Science Theater 2000, episode 404.