Il était une fois la révolution
Exterior filming mostly took place in Andalusia, southern Spain. Some of the locations used previously featured in Leone's "Dollar Trilogy" films; for example, the Almería Railway Station, used for the train sequence in "For a Few Dollars More", returns in this film as Mesa Verde's station. The flashback scenes with Sean and friends were shot in Ireland at Howth Castle in Dublin, and Toner's Pub on Baggot Street, Dublin. As filming progressed, Leone modified the script: as he did not originally plan on directing "Duck, You Sucker", he thought the script was "conceived for an American filmmaker". "Duck, You Sucker!" was one of the last mainstream films shot in Techniscope.