Bryan Singer tweeted that he has cast Peter Dinklage in X-Men: Days of Future Past, adding another big name to a jam-packed cast. But Singer didn't reveal the role the actor would take. The automatic assumption is that he'll play Puck, the dwarf member of Canadian superteam Alpha Flight. That seems reasonable enough, I guess - even though I'm not quite sure Fox has the rights to Alpha Flight (while they debuted in the pages of Uncanny X-Men, the team is not a mutant team, per se. And Puck is not a mutant at all).
To be honest bringing in an actor as good as Dinklage to play a character like Puck - who is not that deep or interesting, and is mostly known for his silly looks - seems dumb. It feels like a major waste. Could Dinklage be playing someone else? I think so, and I think it's a villain.
There are a couple of options. One is Bolivar Trask, the creator of the mutant-hunting giant robots, the Sentinels. That makes some sense, and could be an interesting role. Still, it doesn't feel interesting enough. So here's my wildly uninformed speculation:
What if he's playing Mr. Sinister?
Mr. Sinister is a pretty weird character, but a popular one. He has no involvement in the original Days of Future Past storyline, but that storyline is actually fairly brief. Sinister is this bizarre looking dude:
His deal is that he was a scientist in the 1800s studying evolution, and he made a deal with an ancient and very powerful mutant known as Apocalypse to become an immortal being. Sinister has a bunch of vague powers, including telepathy and telekinesis, and he can control his own body on a molecular level, allowing him to shape-change. He spends a lot of his time mucking about with genetic testing.
I don't think there's ever been a truly great or defining Sinister story (at one point he became a woman, to sort of let you know how the writers keep monkeying with him), but he has an iconic quality. He's known enough to be interesting to use and ill-defined enough to fit into Days of Future Past. There's no way the entire premise of the movie is just 'Stop the assassination of a senator to avoid a bad future.' And by introducing another mutant villain, the film will allow Magneto and Professor X to forge an uneasy truce of some sort (maybe even enough of a truce to explain the Jean Grey recruitment scene in X-Men: The Last Stand!).
What's more, bringing in Sinister opens the door for Apocalypse, who can show up, Thanos-style, at the end of the movie.
Okay, you're saying. I get the story value. But why Dinklage? Isn't Sinister... tall?
Here's where I go off the rails. Recently Bryan Singer said they were playing with the idea of a CGI character in the film. How about a CGI Sinister? The character's weird enough looking to warrant it, especially because just putting a guy in armor and pancake make-up would be lame as hell. What's more, this is where mocap gets really interesting, allowing a good actor to play a role they may not be totally suited for, physically speaking. I think Dinklage could really bring that Victorian-era menace the best incarnations of Sinister has had, and he doesn't need to be six feet tall to do it, any more than Nicholas Hoult needs to be covered in fur to play Beast.
So here's hoping. Puck seems boring. Sinister... there's possibility there.