Carl Copenhagan (played by Rob Walker) is one of the supporting characters for Demo Reel. He is the camera man of East German ethnicity. Not much is known about him, although it may be implied that he worked for the East German secret police.
In The Review Must Go On, it is revealed that the Demo Reel world is in fact a purgatory for the Nostalgia Critic character where he must atone for a lifetime of harsh criticisms. It's therefore possible that Carl and his associate Quinn represent the countless crew members who worked on the kind of movies the Critic reviewed. Carl later appeared in the Demo Reel parody the Cinema Snob did where Braddie found him under some boxes and he helped Braddie film his variation of an E.T Porno, getting into it more then anyone else on set.