In every episode the German town of Bielefeld is mentioned in some way. Bielefeld is known for a comedic urban legend saying that the town doesn't even exist.
As a running joke, Overbeck, second in command in the police's murder squad, seemingly has no first name; everyone just calls him "Overbeck". A girlfriend uses the diminutive "Ovi"once; another time, when asked for his first name he answers "Kommissar. Kommissar Overbeck" (Kommissar being the job title of any police officer). However, some visible letters and door signs suggest his first name might be "Lars".