The producer saw David Hoppe skateboarding on the street and instantly liked the type. He followed him by car and eventually persuaded David's mother to let him and his little brother Fedor be cast for the roles of Robert and Alex. Mrs. Hoppe agreed - on the condition that the could do the catering for the crew.
David Hoppe (Robert) and Julia Martinek (Johanna) had trouble in school, especially in maths and English. Therefore a trailer was set up near the filming locations, decorated with a sign "Schule" (school), where both of them had to spend several hours a week.