ABC added one more member to its Marvel's Agents of S.H.I.E.L.D. Season 2 cast lineup, just days after the network launched a mysterious billboard campaign in Los Angeles, CA.

On Tuesday, Aug. 19, the Hollywood Reporter confirmed that actress Adrianne Palicki will star as secret agent Bobbi Morse - better known as Mockingbird in Marvel fandom. For now, ABC has yet to release details about Palicki's character.

Mockingbird was mentioned amongst a list of confirmed characters in late July, during the 2014 San Diego Comic Con International conference. At the time, ABC did not say who was going to play Bobbi in the upcoming new season of Agent of S.H.I.E.L.D.

In the original comics that inspired the TV show, Mockingbird is a highly-skilled agent adept in both combat and intellectual skills. While in battle, she dispatches her opponents with her pair of steel poles. Due to her scientific background, she is quite intelligent and has a PhD in Biology.

The iconic superheroine has gone through various clothing arrangements since her comic book debut in the early 1970s. So, it is not clear how she will appear in the upcoming second season of the popular TV series.

Meanwhile, ABC has just unveiled yet another teaser billboard in their latest attempt to promote the series. On Monday, Aug. 18, Los Angeles residents were puzzled by a billboard featuring the alien equation that Agent Phil Coulson drew in the first season finale. The formula was recovered by Agent Ward and Skye during a mission in Belarus, in the fourth episode of Season 1.

Indeed, this is not the first cryptic viral ad created by ABC to promote the show. Back in July, the network mounted a glossy-black S.H.I.E.L.D. logo against a matte-black billboard.

Marvel's Agents of S.H.I.E.L.D. Season 2 will premiere on Sept. 23 at 9/8c on ABC.