The film's tagline, "Ya Gotta Believe" (also alluded to in the film), was coined by pitcher Tug McGraw. During the 1973 season, McGraw used the phrase to encourage his fellow New York Mets, who successfully turned around an underdog season to go to the World Series.
The movie centers around the then-California Angels in Anaheim, but was filmed at the Oakland Coliseum due to the fact that the NFL season was taking place and the then-Los Angeles Rams were using the stadium in Anaheim. The Coliseum was not being used as the Raiders had not yet returned to Oakland.
Kit "Hit or Die" Kesey is said to be the "League RBI Champion" when he comes up to bat against Mel Clark. In reality, Carney Lansford (a real 15 season MLB Veteran who played Kesey) never drove in more than 80 runs in any season and averaged just 76 RBIs in a standard 162 game season.
In one scene, George Knox is seen looking through a box of baseball memories and finds his 1979 National League MVP plaque. The actual 1979 National League MVP was shared between Pittsburgh Pirates first baseman Willie Stargell and St. Louis Cardinals first baseman Keith Hernandez.
This film was not the only connection between Disney and the Angels. Two years after the film's release, the Walt Disney Corporation bought the Angels and owned the team until 2003. In addition, Walt Disney himself was one of the Angels original Board Members.