This is straight up, bread and butter MST3K. A 1950s-ish science fiction movie, down in the Z-grade of things, with dodgier science than most, with the air on an asteroid making people small, because of...oh, screw it. The technobabble would make Star Trek weep. Anyways, a spaz-tronaut crashes on the eponymous phantom planet which is just an asteroid with an engine room (basically) and is forbidden to leave for fear of revealing the people living their to those on Earth.
And then they get attacked by space puppies.
Lots of good fun here, but nothing special. Very much a straight, by the books episode, with everything you'd expect. Thoroughly enjoyable, though.