"Agents of S.H.I.E.L.D." executive producer Jeffrey Bell has confirmed that the blue alien appearing in the 'Guest House' is a member of an alien race, originally appearing in Marvel Comics, that will be officially revealed December 2, 2014 in the series episode "Ye Who Enter Here":
The Kree first appeared in Marvel Comics' "Fantastic Four" #65 (August 1967), created by Stan Lee and Jack Kirby.
"...our people don't know anything about the 'Kree' or that there's a planet full of them," said Bell. "What they do know is that the strange carvings created by 'Coulson' after he was injected with the Kree serum are actually the map of a city, and they need to find that city before 'Hydra' does. But where is it? Here or on another planet?"
'Ronan the Accuser', the super-villain of "Guardians of the Galaxy", was also a member of the Kree race.
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