Iain De Caestecker (L) and Elizabeth Henstridge have been cast in Joss Whedon's "S.H.I.E.L.D." television series.

Marvel's casting choices for Joss Whedon's "S.H.I.E.L.D." television series have been played very close to the chest, with only Clark Gregg as Agent Coulson and Ming-Na as Agent Melinda May revealed so far. However, The Hollywood Reporter has announced two new cast members have been added to Whedon's show about the Marvel Universe's premiere peacekeeping force: Elizabeth Henstridge and Iain De Caestecker.

Henstridge is set to play Agent Gemma Simmons, a science whiz, while De Caestecker has been cast as Agent Leo Fitz, a technology guru. THR reports the duo spans most of their time together (mostly bickering) and are "masters at a remarkably young age of their respective fields." If Whedon's previously released cast descriptions are accurate, there are only two more major roles to be filled -- that of Skye, a late 20s woman described as "fun, smart, caring and confident" and Agent Grant Ward, "a quiet one with a bit of a temper."

Whedon will co-write the pilot with his brother Jed Whedon and Jed's wife Maurissa Tancharoen. The pilot is rumored to begin shooting in January, which would put it on track for ABC's fall 2013 season.