Robot Monster (1953)

In which a race of advanced interstellar beings who look suspiciously like gorillas wearing diving helmets with antenna on top, visit Earth and decide that they're going to kill everyone on the planet and then make it a nice vacation getaway for themselves, only to be thwarted by one of their own falling in love with the last remaining woman of legal age on said planet.

Bonus points for unrequited gorilla love, unexplained triceratops wrasslin', incorrect genocidal mathematics, heavy petting in the bushes, and unexplained cave entrance bubbles.