Bud Spencer's character says he can't swim. In real life Bud Spencer was an Olympic swimmer.
In a 1984 interview, director E.B. Clucher stated that the role of Sonny was originally planned for Terence Hill. It's not clear if Hill declined the role because being busy with other works or if there were some contract issues. Giuliano Gemma tried successfully to emulate the typical attitude of Hill in his previous movies with Bud Spencer in order to increase the comic effect.
First movie directed by E.B. Clucher where Bud Spencer doesn't costar with Terence Hill. One year before Terence Hill had made his first movie under direction of E.B. Clucher without Bud Spencer: ...e poi lo chiamarono il Magnifico (1972).