Schlechter Wolf

Schlechter Wolf was a bomb which was deployed during the Blitz by the Nazi German Luftwaffe. It was set to destroy a Chula ambulance as a cover up for Jack Harkness conning the Ninth Doctor and Rose Tyler. However, in order to save their lives so they could help Nancy defeat the Empty Child plague, Jack used his stolen Chula warship to put the bomb in statis. It later detonated in space, destroying the ship shortly after Jack abandoned it to enter the Doctor's TARDIS. (TV: The Doctor Dances)

Behind the scenes
The appearance of the bomb entitled "Schlecter Wolf" is an instance of the Bad Wolf meme. Technically, the closer German translation for the term is "Böser Wolf", the name of the character in the Brothers Grimm fairy tale, "Little Red Riding Hood". "Schlechter Wolf" implies a wolf of inferior quality.