Even though both Terence Hill and Bud Spencer can speak Italian at native level, they are dubbed in the Italian version of this movie by Pino Locchi and Glauco Onorato respectively.
Bud Spencer could really fly an Helicopter since he has the license for both helicopters and planes.
The make and model of the car with Texas number-plates, and horns, lights and a big bull-horn on the bonnet and six spotlights on the front mudguard, was a gold painted 1958 Lincoln Continental Mark III.
The scene in which the two main characters are going to be arrested by the highway cops, a car with an old couple suddenly stops and the woman says "Let's run away, Wilbur". In a scene in Back to the Future (1985) there is an almost identical scene. When Marty arrives to 1955 he tries to stop a car with an old couple inside and the woman says "Don't stop Wilbur, don't stop"
Terence Hill and Bud Spencer play characters mistaken for spies in this spy spoof. Similarly, in their next movie, Miami Supercops (1985), the two play secret agents who go undercover as policemen.