Chicago Cubs
During the 1945 World Series, a man by the name of Vasili "Billy Goat" Sianis attended Game 4 of the series with his pet goat. During the 7th inning of the game, the Stadium's security guards asked Sianis to leave the stadium because his goat was bothering other fans. Sianis became angry and cursed the Cubs, saying that they would never win or even play in a World Series as long as they played at Wrigley Field. Although the curse is often seen as a joke for most Cubs fans, some fans thought it could be the reason for the Cubs' championship drought between 1908 and 2016.  The drought ended and the "curse" was reversed in 2016 when the team won their third World Series title.