It might not be anything. Although it could be one of Dr. Maxis's experiments that did not turn into a zombie or a NOVA 6 Crawler. That's just a guess.
The Call of duty Kino der toten musical Easter egg is Bring me 115 by Eliena Siegman
(keeno-dare-towten)
Walk around it
Tank, Nikolai, Richthofen, and Takeo.
it lets you have three guns