The script is based on a planned 5th "Flatfoot" movie(this time in Brazil) that never materialized. Instead it was changed to become this movie.
When Elliot Vance and Greg Wonder arrive in the office in New York, the magazine on the table next to Vance is actually an issue of German weekly magazine "Der Spiegel", issue no. 15/1984, titled "Der Rheuma-Skandal" (in English: the rheumatism scandal).
The make and model of the white car that was painted up with red flames on then body and white spikes on the tyres was a 1962 Rolls-Royce Silver Cloud II.
The amount of money that Terence Hill and Bud Spencer were contracted for to act as stand-ins was $ 1 million each, plus a fee of $ 500.000 for uncovering the mastermind pulling the strings.