Kinda spoilery below, read on at your own risk:
(..) that glorious little moment when Captain America dropped in. Well, it wasn’t really Captain America. Loki’s gift with illusion allows him to present himself however he wants, and during the scene where he and Thor were on their way out of Asgard, Loki had a little fun with this ability, at one point presenting himself as Captain America. Enter Chris Evans, doing an impersonation of Loki doing an impersonation of Captain America, striding purposefully, he says, “Oh, this is much better! The costume’s a bit much. So tight!” He goes on about how he can “feel the righteousness surging,”
As Hiddleston puts it, “I did an impression of Loki in the Captain America costume, and did the whole performance, and then they showed Chris [Evans] my performance on tape. It’s him doing an impression of me doing an impression of him, and it’s brilliant. Brilliant. I think it’s great.“
Watch video interview here.
Related: my review, it’s related.