In his autobiography, Gene Wilder says that John Wayne was offered the part that was eventually played by Harrison Ford. Wayne loved the role and was eager to work with Wilder. However, an agent tried to offer Wayne less than his usual fee and the legendary actor turned the film down. This may be true, but it is actually unlikely. By 1979, Wayne was too ill with stomach cancer to consider film work, and he died later that year from the disease.
Some viewers have complained that the name Darryl is anachronistic. One etymology source says that, as a first name, it was not used by English speakers until the late nineteenth century. However, the name comes from Old French "d'Airelle", meaning someone from the town of Airelle in France. Airelle itself means "open space", from the Latin, so it might be quite old.
The Frisco Kid (which stars Harrison Ford) has a scene in which an Orthodox Jewish man mistakenly assumes that Amish men are fellow Orthodox Jews. In Witness (also starring Harrison Ford), an Amish boy assumes that an Orthodox Jewish man is a fellow Amish man.
1979 marketing for the film heavily emphasizes Gene Wilder's role in the film, with little marketing of Harrison Ford's supporting role, despite Ford having been in the blockbuster Star Wars two years earlier. When The Frisco Kid was released on DVD, the cover was a blow up of Ford's face, with Wilder relegated to a small corner of the cover.