So ein Flegel (Such a Rascal) is a comedy film, a precursor to the 1944 version Die Feuerzangenbowle, about a playwright, Hans Pfeiffer, who trades places with his student brother Erich to gather material for a play about high school life. The film, starring Heinz Rühmann in both Pfeiffer roles, explores the comedic results of this role reversal.