The Twitter account follows all the right people you’d expect, from Marvel franchise stars to Community cast members (the brothers directed and produced the comedy series), but it’s the people who are following the account that add credence to its authenticity.
Some of the early followers (on an account that only had 31 of them when it was discovered) include Jason Stamey, who has worked in casting on nearly all of the Marvel movies, Ryan Stankevitch, the vice president of global marketing for Disney and Andrew Stamm, a directors and producers assistant currently credited with working on Captain America: Civil War. Those are three rather strange and coincidental followers to be paying attention to this account if it’s just some kind of fan created hoax.