Oh, the irony. Comic Vine maniacs frustrated by the creative license FIRST CLASS is taking with the X-Men’s chronology will surely appreciate knowing that, unlike the five others young mutants in the movie, Beast was actually a member of the “real” first class in the comics.
The character’s evolved significantly since his days in that "real" first class, of course.
Hank McCoy debuted in X-MEN #1 in the late summer of 1963 (the same year FIRST CLASS is set in!) His gimmick was basically that he was a hairless, incredible-agile gorilla man who also happened to be absurdly smart. While his hunched posture and over-large hands and feet made him look simian in these early appearances, a series of “secondary mutations” made him look progressively more feline over the years as he’d adventure with the likes of X-Factor, the Defenders and even the Avengers in addition to the “strangest super-heroes of them all.” His genius-level intellect would remain a constant, though. Goes to show all you maniacs: brawn comes and goes, but smarts are forever.
Beast has actually shown up a few times in the movies already. His first appearance was a quick cameo on a TV in X2 as a talk-show guest chatting up mutant affairs and he was a major player in THE LAST STAND. The latter movie established him as mutantkind’s de facto ambassador to human America: an ex-X-Men who’d put aside adventuring for politics at some indeterminate point in the past. Eventually, he'd master government dealings enough to became the president’s Secretary of Mutant Affairs.
By X3, Beast is comfortable and proud of his feral mutation, walking around freely in public without fear of embarrassment or harassment. The Beast of X2, however, doesn’t have a single blue hair on him and, while that’s logically explained by the crew changing ideas between movies, it’s fun to interpret the discrepancy as being a result of a disguise (perhaps a holographic one, as he's often used in the comics.) Believe it or not, speculating on that actually gives a greater context for his arc in the new movie.
The character profile trailer on Beast reveal that he'll have a romance with Mystique. Though, they’re both blue and monstrous in the comics, they’ve never had anything close to a romantic relationship before. Hank’s dated various human girls while Mystique’s had trysts with Sabretooth, Azazel, Forge and even Destiny. It looks like her arc in FIRST CLASS will see her growing more comfortable with her scaly, natural appearance while, conversely, Beast’s attempts to suppress his own abnormalities backfire on him.
About ten years after his debut in the comics, Beast often disguised himself with a serum injection that accelerated mutation and gave him a furry coat. He'd use a second injection to reverse the transformation but, after waiting too long to administer it once, he was stuck with the fur permanently. The trailers hint at something similar to this, as we see Hank struggling to suppress a fast-acting transformation after dropping a syringe. Presumably, he’s trying to repress the more extreme parts of his mutation with a serum until, ultimately, his own nature wins out.
In the trailers, Hank and Raven bond over a mutual desire to “be normal” even though, later on in the movies' timeline, they end up embracing their monstrous appearances. It seems, then, that the choice is involuntary for one and voluntary for the other. Considering how no history between the two is ever alluded to in THE LAST STAND and how Mystique made such a strong declaration to Nightcrawler in X2 about how she shouldn’t ever have to disguise herself, I suspect their romance will be short-lived; broken off by a disagreement on the value of “hiding.” Tragically, Mystique may be driven into the arms of Azazel while Beast will only come to peace with his appearance in middle age.
That’s my conjecture, anyway. We'll find out how on-the-mark it is come June 3rd.