When the brothers, both stoned, drive on the Autobahn at night, the car seems to fly. It shows the license plate "DU-DU" (DU for Duisburg), same as the VW Beetle "Dudu" from the German 1970s "Käfer" movie series (inspired by the US "Herbie" movies).
Originally, the screenplay was set in Oberhausen. It was changed to Duisburg because the film team found several locations in Duisburg that had hardly changed since the 1960s. It seems that Duisburg city authorities were not happy to hear that.
The movie was planned bilingual: Depending on the situation, actors would speak Italian or German, just like immigrants are used to. Italian dialogue would then be subtitled. However, the production company insisted on a dubbed, completely German version. This makes for some odd moments, like the mother not understanding what the doctor says although they obviously both speak the same language. It also loses information, like the fact that the father talks Italian to his sons while they respond in German. The bilingual version is contained in the DVD.