Marvel Studios' Avengers stars Robert Downey Jr. and Mark Ruffalo wish their fellow Marvel Cinematic Universe superhero actor Chris Evans a happy birthday. All three actors have been main stars of the MCU since Phase 1, with Downey kicking off the franchise as Tony Stark in Iron Man, followed by Evans debuting as Steve Rogers in Captain America: The First Avenger while Ruffalo took over the role of Bruce Banner from Edward Norton for The Avengers. Downey and Evans each led of trilogy of Marvel movies as Iron Man and Captain America, respectively, in addition to uniting with other superheroes for all four Avengers films.

However, their characters' stories came to an end in this spring's Avengers: Endgame, with Iron Man dying to save the universe from Thanos and Captain America going back in time to have the life he missed by sacrificing himself at the end of The First Avenger. As for Ruffalo's Smart Hulk, he remains alive and well in the MCU, though it's unclear whether he'll return in a future movie. Nevertheless, after working together on a number of movies over the past 10 years, Downey, Ruffalo and Evans are undeniably good friends. So it makes sense the MCU stars would wish each other happy birthday.

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Today, June 13, marks Evans' 38th birthday and his MCU co-stars are celebrating the Captain America actor with heartfelt and funny posts on social media. Ruffalo took the opportunity to post a new behind-the-scenes photo of himself with Evans, while Downey went full Tony Stark and cracked a joke about Captain America's ass. See both posts below.

Additionally, Evans himself took to social media to thank friends and fans alike for their birthday wishes, taking the chance to give a little bit back to the Twitter community by revealing another of his early headshots. This time, Evans dons a velour Sean Jean tracksuit and the actor questions his young self's decisions. See the post below.

While Evans' time as Captain America in the MCU may be over, his friendship with fellow Avengers stars like Downey and Ruffalo lives on. And thanks to that friendship, fans of the Marvel franchise can look forward to hopefully many more years of social media jokes among the stars. Perhaps one day they'll all reunite on screen in some form - Hollywood does love their reboots and revivals. Or, like Evans' idea of a buddy cop movie with Chris Hemsworth, they could appear together in other, non-superhero projects. For now, though, fans will have to settle for the social media love among the Avengers stars.

Still, the legacy of their characters will persist as Marvel Studios heads into Phase 4 with no sign of slowing down. The Captain America mantle was passed to Sam Wilson (Anthony Mackie) who will star in a Disney+ TV show along with Winter Soldier (Sebastian Stan). Plus, Smart Hulk survived the battle of Thanos and Tom Holland's Spider-Man will take up Iron Man's role as Earth's main protector in this summer's Spider-Man: Far From Home. Evans and Downey may be done with the MCU, and Ruffalo's future may be unclear, but they won't be forgotten - especially since the Avengers stars continue to showcase their friendship on social media.

Next: Every Upcoming Marvel Cinematic Universe Movie

Source: Robert Downey Jr., Mark Ruffalo, Chris Evans

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