In Marvel comics Wonder Man's alter is an actor named Simon Williams. Simon ends up getting involved in a super human project that gives him awesome energy based powers. Simon is a character that at certain times is a villain faced by the Avengers and at other times has been a proud member of the team. Nathan Fillion may be the Simon Williams of the Marvel Cinematic Universe and show up in Guardians of the Galaxy 2.
Update May 17, 2017
James Gunn cleared up the Nathan Fillion posters in Guardians of the Galaxy and why they were cut. He explains the scene on his Facebook. I think one important thing is that this is considered canon by Gunn which does make Fillion Simon Williams.
As many of you know one of my best friends in the world is Nathan Fillion. Along with Michael Rooker and Gregg Henry he's been in every movie I've directed - even as a monstrous, perverted voice in Guardians of the Galaxy. I didn't have a good cameo for him in Vol. 2 - and I wanted to bring him more fully into the MCU at some point, so I didn't want to make him Aakon Guard #2, narrowing his chance of a more substantial role in the future. I really do love the character of Simon Williams/Wonder Man in the comics - a sometimes douchey actor/superhero - and could see Nathan clearly in that role (not because he's a douchebag but because he's great at playing one). But, of course, in a movie set 99.9% in space I didn't really have a place for him. So in a small flash to earth I decided to put a theater playing a "Simon Williams Film Festival," with six Simon Williams movie posters outside. Obviously, from the posters, he's had a run of B movies. Most of them in themselves are Easter eggs of some sort or another. Unfortunately, the small section of the scene where they appeared slowed down the movie and I had to cut the Easter eggs from the film (along with storefronts named after comic book luminaries Starlin, Mantlos, Annett and others). Equally a bummer was that a lot of people took photos of these posters on the day so suddenly every fan site was reporting that Nathan was playing Wonder Man in he movie. He was even the third-billed actor on IMDB!
So that's the full story. Nathan's only cameo in the movie ever were these posters. I'll post them all over the next few days.
And, yes, I think we can consider them canon for the MCU, and I hold onto hope that Simon Williams will rise again!!
We may not get Fillion in a scene but it seems that one was filmed. In it Fillion seems to be actor Simon Williams playing a cosmic explorer in a film. Fillion recently posted a picture of the scene on his Instagram and says that it will not make it into the film.
Wonderman is known for having some of the most awesome powers of the Avengers but also the most mental instability. He suffers from cowardice, paranoia and selfish narcissism. His massive powers though have made him an important part of many Avengers teams.
Who is Wonder Man?
Nathan Fillion appeared in the Klynn (Space jail) scene of the Guardians of the Galaxy. Now he will also appear in movie posters of Simon Williams (Wonder Man) in Guardians of the Galaxy Volume #2.
No one knows exactly how much Simon Williams will appear or even if he will be Wonder Man. However, look out Fillion is a popular actor and he would certainly make many people happy taking on a more substantial part in the Marvel Universe.
My guess is at some point we will see Wonder Man!
Here are the fake movie posters for the Simon Williams Film Festival. One is a Tony Stark biopic that seems to be similar to the real version of Jobs. There is also a poster of Arkon who is a Marvel character that is a bit like Conan.
Who is Arkon?
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