unhistorical:

May 25, 1977: Star Wars is released.

Before the release of his first Star Wars film, George Lucas was convinced  that his genre-busting space opera epic would flop at the box office, so he made a bet with Steven Spielberg, whose science-fiction film Close Encounters of the Third Kind was also set to release that year. If Spielberg’s film made more money than his own, he would collect a percentage of whatever profit Close Encounters made, and vice versa. Spielberg’s sci-fi classic made an impressive $337 million by the end of its run, but Star Wars made nearly $800 million which, adjusted for inflation, makes it the third highest-grossing film of all time (it also spawned a franchise which, according to some estimates, has yielded a total revenue of $27 billion). Needless to say, Spielberg lost the battle of films but won the bet, and reportedly continues to benefit from that bet today.