Who she is: Darcy Lewis
Her power: No powers, other than a generally delightful demeanor.
Her story: Darcy begins Thor as an intern to Jane Foster, a political science student who happened into the position by virtue of being the only applicant. While she’s by Jane’s side for most of the events of that film, her primary role is to supply arch commentary on what’s happening, be it Thor’s arrival, adjustment period, or his confrontation with the Destroyer at the film’s end. By Thor: The Dark World, Darcy has graduated to being able to hire an intern of her own, Ian, and travels with Jane to London to aid Erik Selvig in his work on new cosmic anomalies. When Thor takes Jane to Asgard to deal with her possession by the Aether, Darcy and Ian hunt down Selvig, and when Thor and Jane return, the five of them work together to defeat Malekith and the Dark Elves when they arrive on Earth.
Played by: Kat Dennings
Currently, Darcy is: Probably still working with Jane Foster.
Where will we see her next? Unknown. Jane isn’t playing a role in Thor: Ragnarok, which makes it highly unlikely Darcy would appear, either. Maybe she could have her own film?