Marvel fans yearning for “Marvel’s Agent Carter” will be thrilled to see Peggy Carter herself guest-star in the “Marvel’s Agents of S.H.I.E.L.D.” Season 2 premiere, Entertainment Weekly reports. Hayley Atwell will appear in the first episode, but fans aren’t exactly sure how she’ll appear.

Agent Carter was Captain America’s girlfriend before he was frozen, so she is from the 1940s. But she's much more than Steve Rogers' old flame. Peggy helped start S.H.I.E.L.D. with Howard Stark (Iron Man’s father). Obviously, she never intended for the Nazi-influenced Hydra to infiltrate the organization, but Coulson will be helping to rebuild S.H.I.E.L.D. and trying to bring the organization back to it's roots. Coulson would absolutely know who Agent Carter is — especially since he is a Captain America fanboy — and he’ll try to return S.H.I.E.L.D. to what Carter and Stark intended it to be.

Executive producer Jeff Bell acknowledged that Coulson would be bringing back a vintage S.H.I.E.L.D. “Coulson was always interested in getting back to the roots of S.H.I.E.L.D.,” Bell told TV Line. “To the kind of organization it used to be — you know, this small, covert, ‘men in black’ kind of thing. And I think you get a feel for that when we come into the second season.”

While the present-day Peggy could appear as an elderly woman the way she did in “Captain America 2: The Winter Soldier,” she could also appear as the 1940s version of herself. In the present, Peggy isn’t in great health. The last time Captain America saw her, she appeared to be suffering from dementia and was in a hospital, so her actions in “Marvel’s Agents of S.H.I.E.L.D.” would be limited. But the show could go back to the past.

Since “Marvel’s Agent Carter” will follow the 1940s Peggy, that’s the version that will most likely appear as ABC and Marvel probably want to promote the show. Peggy could come to Coulson in a dream or a flashback to the history of S.H.I.E.L.D. A flashback would help connect the show to “Marvel’s Agent Carter,” which will premiere in the “Marvel’s Agents of S.H.I.E.L.D.” timeslot when the show goes on hiatus this winter. The guest appearance would be a great opportunity to show Peggy in action, but the guest appearance will probably be a cameo rather than an entire episode featuring her. The premiere, titled “Shadows,” will already be packed with plenty of other action, as seen in the Season 2 trailer. Peggy wouldn't be the only one with a cameo. Also making a cameo as himself in the Season 2 premiere is George Stephanopoulos from ABC News, TV Guide reports.

Atwell and Stephanopoulos join several other high-profile guest stars for Season 2 including Kyle MacLachlan, Adrianne Palicki and Lucy Lawless.

“Marvel’s Agents of S.H.I.E.L.D.” Season 2 will premiere on ABC on Tuesday, Sept. 23, at 9 p.m. EDT. What do you think Agent Carter will do in the episode? Share your theories in the comments.