The Parent Trap (1961)
You know and love the 1998 version with Lindsay Lohan, but have you ever seen the original? At least one thing remained constant between this film and its remake: the twins are played by just one actor.
E.T. The Extra Terrestrial & His Adventures on Earth (1982)
Steven Spielberg's '80s hit was practically required viewing during the childhoods of many—but how many years have passed since you last watched it?