One of the biggest mysteries surrounding Marvel's "Agents of S.H.I.E.L.D." is how Agent Coulson (Clark Gregg) came back from the dead after being killed by Loki in "The Avengers."

Alex Zalben from MTV News interviewed "S.H.I.E.L.D." executive producer Jeffrey Bell about the series and asked about the mystery that has comic fans scratching their heads.

"As Coulson comes to this questioning what's happened, that's really interesting story stuff for our character," Bell told Zalben. "That to us was something that pays off much better than the holy s--t of it, because there's only so many holy s--ts it could be. That said, I hope we have a cool holy s--t."

While some have criticized "S.H.I.E.L.D." for being boring and uneven, as time goes on Coulson's mystery has become a central and intriguing part of the series.

Bell explained to Zalben that the creative team behind "S.H.I.E.L.D." has had a plan all along. "My hope is that the arc of these characters is something people care about," said Bell, "and we'll continue to work on that."

What do you "S.H.I.E.L.D." fans think happened to Coulson? Let us know in the comments.

"Marvel's Agents of S.H.I.E.L.D." airs Tuesdays at 8 p.m. EST on ABC.

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