Agent Carter trailer Hayley Atwell (center) will guest star on "Marvel's Agents Of S.H.I.E.L.D." Season 2 for the second time this year in episode 8. Photo: ABC/Kelsey McNeal

UPDATE: The original article incorrectly stated that Lou Ferrigno Jr. played the Hulk. It was, in fact, his father Lou Ferrigno who played the Hulk in "The Incredible Hulk" TV series.  

Marvel’s Agent Carter” fans won’t have to wait very long for their next glimpse of Peggy Carter (Hayley Atwell). She will be guest starring on “Marvel’s Agents Of S.H.I.E.L.D" Season 2 episode 8, Marvel recently announced. They conveniently left out any details on what Captain America's former flame will be doing, but the synopsis gave us enough clues to guess that Peggy will likely appear in another flashback. We have a few theories about what could be included in the flashback.

The episode will reportedly feature an “epic face-off against Hydra to uncover an ancient secret.” S.H.I.E.L.D. and Hydra have plenty of other secrets, but both organizations started back in WWII. Anything “ancient” likely only goes back to Peggy’s time.

While no one can say what the secret is about, it could have to do with the obelisk. Everyone has wanted the mysterious obelisk, the first 084 S.H.I.E.L.D. ever found, captured by Agent Carter herself. Yet, no one, except Skye's father, can figure out how it works.

The “Marvel’s Agents Of S.H.I.E.L.D.” Season 2 premiere started with a flashback to Peggy Carter taking the 084 from Daniel Whitehall (Reed Diamond), known then as Werner Reinhardt. Interestingly, Reed’s guest starring role is credited as Daniel Whitehall/Werner Reinhardt for the first time this season. It would seem that he’ll be featured in a flashback to his past as a Nazi officer.

While we can’t be sure exactly what any flashbacks would include, the “Marvel’s Agent Carter” trailer made it clear that Peggy can take care of herself. While last time she easily arrested Whitehall/Reinhardt without much of a fight, there might be a little more action this time to excite viewers for “Marvel’s Agent Carter’s” January premiere.

While Hayley Atwell is certainly the most buzzed-about guest star, she isn’t the only familiar name in the episode. Lou Ferrigno Jr. will also make an appearance as Agent Hauer. No word on if he is a Hydra agent or a S.H.I.E.L.D. agent -- but longtime Marvel fans know that his father was an Avenger. Lou Ferrigno is best known for playing the Hulk on "The Incredible Hulk" TV series from 1977 to 1982. Fans of co-creator Joss Whedon’s previous TV shows will see another familiar face. “Dollhouse” alum Dichen Lachman will guest star as an unnamed young woman.

Watch Agent Carter’s first appearance on “Marvel’s Agents Of S.H.I.E.L.D.” below:

“Marvel’s Agents Of S.H.I.E.L.D.” Season 2 episode 8 airs Tuesday, Nov. 18, at 9 p.m. EST on ABC. Why do you think Agent Carter is coming to the ABC show? Is she involved in this “ancient secret”? Share your thoughts in the comments section below!