Matt Damon
There’s something kind of dopey about Birdperson, which is why Matt Damon would be the perfect fit. It’s not that he’s unattractive or anything, but he isn’t one of those stand out from the crowd kind of guys, either. Plus, we’ve already seen Matt Damon in every kind of weird space suit there is, so Birdperson’s armor would be a very logical next step in his costuming career.