The two intoxicated men sliced open several of their fingers down to the bone, a police spokesperson in Neumünster said.
A third participant in the ritual sustained an "acceptable and blood brother appropriate cut on his finger," the spokesperson said.
It was unclear whether the three men, between 18 and 31-years-old, had attended the premiere of a new interpretation on Karl May's "Winnetou and Old Firehand" in Bad Segeberg some 30 kilometres away.
Karl May is one of Germany's all-time best-selling authors. His pulp novels, written around the turn of the 20th Century, played heavily on stereotypes about America's Wild West and Native Americans. Many of his novels were filmed as movies in a style that helped influence the Spaghetti Western genre.