Irish comedic actor Chris O'Dowd has confirmed to Indiewire that he's shot a scene for Thor: The Dark World. He had been previously unannounced which will likely be the case for the majority of the smaller roles in the film. The question is, factoring in his high profile could Chris be playing an actual Marvel character in the film?
"I think I'll do more dramatic stuff and I think I have some stuff coming out that's a bit more dramatic. I don't know if I'd do an action movie because I don't know if I could keep a straight face honestly, I just think it's so silly. Like I love watching them but I can't imagine me doing one. Actually, you know what I've done, just for fun because I didn't think there was any way that I could be in a superhero movie, so I've done a scene in the new "Thor" movie, just for that. I just do like one scene, which was quite fun."
One theory is that he could be playing Jane's ex-boyfriend Dr. Donald Blake who was mentioned in the original film. Along with being at least close to Thor's height which Chris could pull-off. Blake in the comics is Thor's alter ego and fragile human form (having a mobile disability).
Another possibly could be Dr. Stephen Strange aka Doctor Strange. It's expected that Strange will be likely cast by a European actor and talk over the Summer via ThePlaylist that Strange could show up in the sequel has been mentioned by a couple different sources. Considering his high profile it wouldn't be hard to see Marvel quietly casting O'Dowd in that role or even Ant-Man's Dr. Hank Pym for that matter. Since The studio has a tendency to hire actors named Chris for their lead roles (Hemsworth, Pratt and Evans). However, it seems like Blake is the most likely role he's taken as Chris downplays ever starring in a action film.