In 2005, Kross came to the attention of Detlev Buck through his daughter, Bernadette, and he auditioned for Tough Enough (Knallhart); Buck hired Kross to play the lead, a 15-year-old boy who moves with his mother from a rich neighborhood of Berlin (Zehlendorf) to the Neukölln area, known at the time for its high number of Turkish immigrants and high crime level.