Save the Green Planet! (Korean title: 지구를 지켜라!, Jigureul Jikyeora!) is a South Korean science fiction comedy film written and directed by Jang Joon-hwan, released on 4 April 2003. Synopsis: A deranged man kidnaps another man, convinced that the latter is a space alien.

References:
https://en.wikipedia.org/wiki/Save_the_Green_Planet!