[1][4] Haddix picked up the Game Seven win in the 1960 World Series, pitching in relief when Pirates second baseman Bill Mazeroski’s walk-off home run earned Pittsburgh the title.

He was nicknamed "the Kitten" in St. Louis for his resemblance to Harry "The Cat" Brecheen, a left-hander on the Cardinals during Haddix's rookie campaign.

[2][6] However, Braves pitcher Lew Burdette was also pitching a shutout,[4] which was seriously jeopardized on only three occasions: the 3rd inning, when a Milwaukee base-running blunder negated three consecutive singles; the 9th, when Pittsburgh finally advanced a runner as far as third base;[3] and the 10th, when Pirates pinch hitter Dick Stuart came within a few feet of a two-run homer.

A fielding error by third baseman Don Hoak ended the perfect game in the bottom of the 13th, with the leadoff batter for Milwaukee, Félix Mantilla, reaching first base.

[4][8][9]I could have put a cup on either corner of the plate and hit it.Haddix's 12+2⁄3-inning, one-hit complete game, against the team that had just represented the NL in the previous two World Series, is considered by many to be the best pitching performance in MLB history.

"[4] After the game, Haddix received many letters of congratulations and support, as well as one from a Texas A&M fraternity which read, in its entirety on university stationery, "Dear Harvey, Tough shit."

"[4] In May 1989, Milwaukee's Bob Buhl revealed that the Braves pitchers had been stealing signs from Pittsburgh catcher Smokey Burgess, who was exposing his hand signals due to a high crouch.

[14][15] From their bullpen, Braves pitchers repeatedly repositioned a towel to signal for a fastball or a breaking ball, the only two pitches Haddix used in the game.

[1] In 1964, Haddix served solely as a relief pitcher for the Orioles, pitching 89⅔ innings, with five wins, ten saves, and a 2.31 ERA.