Youppi! (whose name means Hooray! or Yippee! in French) was the Montreal Expos mascot starting in 1979 until the team moved to Washington, DC after the 2004 season. During that period, he was the most popular figure associated with the team and did extensive charity appearances around the province of Quebec, as his popularity transcended that of baseball. Because of his close ties with the local population, it would have been unthinkable to have him move to another city; instead, he was "adopted" by the Montreal Canadiens of the National Hockey League and became that team's mascot.
Youppi! replaced the short-lived Suki, a humanoid mascot that made a brief appearance in 1978 and was not liked at all. The brainchild of team Vice-President Roger D. Landry and employee Rodger Brulotte, Youppi! was designed by the company that made the famous Jim Henson muppets and was immediately adopted by hometown fans (it helped that the Expos had their first winning season in 1979). He was known for walking on top of the opposite team's dugout and getting the fans excited by mock-sliding into bases painted on the dugout roof, at a time when the Expos were an aggressive baserunning team. He had a variety of costumes he would wear for special occasions, such as a formal vest and top hat for ceremonial days, and a pyjama he would put on when a night game went deep into extra innings.
Youppi! was famously ejected from the longest game in Expos history, on August 23, 1989, when Los Angeles Dodgers manager Tom Lasorda complained to the umpires about the racket he was making. As per his custom, when the game went into extra innings, he put on his pyjamas and nightcap, brought a huge pillow and went to sleep atop the opposing team's dugout. But in the 11th inning, Lasorda, who was still upset over some controversial calls made earlier in the game, complained about the supposed racket his upstairs tenant was making, and got umpire Bob Davidson to eject Youppi! from the game, which was not decided until the 22nd inning.
In 2014, Youppi! was involved in a bet with Late Night host Jimmy Fallon. The bet was to have the loser of the NHL's Eastern Conference Finals wear the winner's sweater. The New York Rangers won 4 games to 2 and Youppi! took to posing around Montreal landmarks wearing a Rangers sweater and looking dejected. On June 14, 2020, Youppi! was inducted into the Mascot Hall of Fame.