The 69-year-old actor revealed that he has shot for secret role in the Taika Waititi-directed Marvel movie, reported Entertainment Weekly.
"I 'm not really allowed to say this and I can't tell you what it is...I did a couple of days on Thor just before I came over here. I had to sign all sorts of things. So if I say anything else, Marvel's secret agents - and they are lethal - will come and get me and probably my children, as well," Neill said.
Featured in the cast are Chris Hemsworth as Thor, Tom Hiddleston as Loki, Idris Elba as Heimdall, Anthony Hopkins as Odin, Cate Blanchett as Hela, Mark Ruffalo as Bruce Banner/Hulk, Karl Urban as Skurge, and Tessa Thompson as Valkyrie.