07/30/2013 01:54 pm ET

How 'Agents Of S.H.I.E.L.D.' Kept A Big Secret


Fans lucky enough to attend the "Marvel's Agents of S.H.I.E.L.D." panel at Comic-Con last week were privy to one of the best-kept secrets in the Whedonverse: Minutes into the screening of the series premiere, Cobie Smulders made a surprise cameo, reprising her Avengers role as Agent Maria Hill.

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