The Fullmetal Alchemist group would NOT prop Tony
On the surface, it seems like Edward Elric and Roy Mustang of Fullmetal Alchemist are Tony Stark clones: Edward is quick-tempered and strikes out at others, while Roy is focused on his own glory. Both men are known to be self-serving if they are not personally affected. But Edward is known for being brutally honest and unimpressed with egotistical people, while Roy is concerned with making sure things are done right. Neither man seems likely to prop Tony Stark, but very likely to call him out.
Note: I've never seen Fullmetal Alchemist, so the characters may not be in character.
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Roy and Edward were just finishing a meeting when Iron Man burst into the room. The armor's faceplate flipped up and Tony Stark said, "Just the alchemists I was looking for. Listen, the Avengers roster is a little bare right now, so I'm going to need you to step up and fill the gaps."
Roy and Edward looked at each other. Edward asked, "Did you invite this creep?"
Roy shook his head and said, "I have better taste than that."
Edward stood up and said, "Get out of here, Stark."
Tony said, "Make me."
Edward smirked and said, "You REALLY want to rethink that."
He took a step forward and said, "You get permission to come here? Because I'm pretty sure you crossed quite a few international borders. You seriously think for one SECOND that any alchemist would sign the Sokovia Accords? Especially to be on a team with YOU?"
Tony backed up a step as Edward took another step forward.
Edward said, "You've had WAY too many chances in your miserable life. Instead of learning from ANY of them, you just keep making the same mistakes over and over. Half your team just disappeared--where are they? In jail? Or on the run from YOU? Think about why hardly anyone is on your side. You made the wrong call."
From his seat, Roy smirked. He said, "What he said. I suggest you leave, Stark, before Edward decides to crush you like any other empty can."
Stark left as quickly as he came.