1. The titular "planet" is Earth.
Movie: Planet of the Apes (1968)
Writer: Rod Serling and Michael Wilson
It should come as no surprise that the greatest twist ending of all time was written by Rod Serling—after all, he's the same mastermind who created The Twilight Zone, the venerable breeding ground for mind-blowing twists and unforeseen narrative turns.
The ending of the 1968 sci-fi classic Planet of the Apes is such common knowledge nowadays that it's difficult to process just how brain-melting it was for audiences back in '68, but let's try to put ourselves in their shoes: You're watching a movie about an American astronaut, George Taylor (Charlton Heston), who crash-lands on a distant planet that's inhabited by talking and civilized apes, and everything about it says that the setting is located somewhere else in our galaxy.
And when Taylor and gorgeous cave woman Nova (Linda Harrison) ride off into the sunset on horseback, having escaped the tyrannical primates' clutches, Taylor notices a large object sticking out of a beach's sand, and not just any old object—it's the top-half of the Statue of Liberty. He's been on a future, post-nuclear-war Earth all along. “Goddamn you all to hell,” he shouts in a fit of fiery sadness. He's clearly unaware that, 33 years down the line, Tim Burton will direct a painfully bad Planet of the Apes remake. Had he known, there surely would have been more curse words in that statement.