Iain De Caestecker and Elizabeth Henstridge explore the relationship between their characters Agents Fitz and Simmons in the latest featurette for Marvel's Agents of S.H.I.E.L.D., following the Agent Grant Ward featurette that debuted last week. Iain De Caestecker's Agent Fitz is S.H.I.E.L.D.'s gadget expert, while Elizabeth Henstridge's Agent Simmons is the biochem expert, both of whom have a quirky brother-sister type of relationship. Created by Joss Whedon, Jed Whedon, and Maurissa Tancharoen, Marvel's Agents of S.H.I.E.L.D. debuts Tuesdays this fall on ABC. The network has not announced when the series premiere will air yet, so stay tuned.