Answer:
It has happened 11 times. The comeback teams were:
• The 1921 New York Giants over the New York Yankees, 5-3.
• The 1955 Brooklyn Dodgers over the New York Yankees, 4-3.
• The 1956 New York Yankees over the Brooklyn Dodgers, 4-3.
• The 1958 New York Yankees over the Milwaukee Braves, 4-3.
• The 1965 Los Angeles Dodgers over the Minnesota Twins, 4-3.
• The 1971 Pittsburgh Pirates over the Baltimore Orioles, 4-3.
• The 1978 New York Yankees over the Los Angeles Dodgers, 4-2.
• The 1981 Los Angeles Dodgers over the New York Yankees, 4-2.
• The 1985 Kansas City Royals over the St. Louis Cardinals, 4-3.
• The 1986 New York Mets over the Boston Red Sox, 4-3.
• The 1996 New York Yankees over the Atlanta Braves, 4-2.