In the days of the Internet, there’s only very rarely a “secret” or “surprise” appearance by a character in a movie. Idris Elba and Tom Hiddleston’s cameos in Avengers: Age of Ultron no longer fit the bill.
That’s thanks to an interview with Telegraph, in which Elba spilled the beans. “I’m in Avengers,” he said, going on to say, “I’m doing a scene with Chris Hemsworth and Tom Hiddleston.”
Of course, Heimdall and Loki appearing is perhaps even bigger spoiler than the actor might have thought; at the end of Thor: The Dark World, Tom Hiddleston’s Loki was presumed dead, but had actually taken the spot of Odin (and his form) on the throne of Asgard. Appearing as Loki with Heimdall and Thor (assuming that's the case) prior to Thor: Raganarok, the recently announced third solo chapter for the Norse God of Thunder is a major spoiler.
As for anyone holding out hope that Elba will take on a larger superhero role, it seems the actor isn’t too keen on the intricacies of the scenes and work required. Talking about reshoots he had to do for the second installment, Elba said they were “torture.”
”I’m actually falling down from a spaceship, so they had to put me in harness in this green-screen studio. And in between takes I was stuck there, fake hair stuck on to my head with glue, this f------ helmet, while they reset. And I’m thinking: ‘24 hours ago, I was Mandela’.”