William Bendix had been a bat boy at Yankee Stadium during the early 1920s, and had personally seen Babe Ruth hit over 100 home runs. Bendix was fired from his job after fulfilling Ruth's request for an order of 15 hot dogs and sodas before a game. After consuming the huge order, Ruth developed gastritis and was unable to play that day, resulting in a Yankee loss.
The scenes at Yankee Stadium were shot and filmed just hours before a real baseball game was scheduled to take place, and Babe Ruth got up from his death bed just long enough to see it while he was still alive.
The film was rushed for release while Babe Ruth was still alive, which is why the movie ended the way it did. George Herman Ruth attended the movie's premiere on Monday, July 26th, 1948. He died 21 days later on Monday, August 16th, 1948, 3 weeks before the theatrical release on Monday, September 6th, 1948.
William Bendix, who was borrowed from Hal Roach's company to appear in the film, was chosen by Babe Ruth himself.