The shop's name can be roughly translated as "great mischief" and it's a paradise for comic fans!
Their offer ranges from mangas/anime from Japan (it's actually the biggest part of the collection) to good old traditional comics from all over the world (eg. "Tim and Struppi" etc etc etc).
There are books, DVDs, games, magazines and lots of other fan items, so that comic- or manga-addicts get their money worth.
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The other "Grober Unfug"-shop in Berlin is located in Kreuzberg (Zossener Strasse 33, U-Bahn Gneisenaustrasse).