Led by Robert Downey Jr., the cast of Avengers: Endgame paid tribute to Josh Brolin by singing him Happy Birthday. Brolin, who plays Thanos in the Marvel Cinematic Universe and was the big bad of the most recent Avengers movies, recently celebrated his 52nd birthday on February 12. To commemorate the occasion, Iron Man/Tony Stark actor Downey shared a video from production that features a large grouping of the cast singing to him for his birthday, which happened when the movie was still shooting.

Robert Downey Jr. shared the clip on Instagram. The video features a massive grouping of MCU stars including Chris Pratt (Star-Lord), Chris Hemsworth (Thor), Tom Holland (Spider-Man), Chris Evans (Captain America), Mark Ruffalo (Hulk), Chadwick Boseman (Black Panther), Anthony Mackie (Falcon), Danai Gurira (Okoye), Evangeline Lilly (Wasp), Elizabeth Olsen (Scarlet Witch), Pom Klementieff (Mantis) and Sean Gunn, who serves as the stand-in for Rocket during filming, in addition to playing Kraglin in the Guardians of the Galaxy movies. Even co-director Anthony Russo managed to get in on the action.

A shorter version of this video had been released previously, but it wasn't clear at the time that the cast was singing to Josh Brolin. Robert Downey Jr. released the shorter version on the 11th anniversary of the first Iron Man. Brolin isn't seen in the video, but one has to imagine it made the man behind the Mad Titan smile. The actor will next be seen in Denis Villeneuve's highly-anticipated Dune remake later this year. As far as Thanos goes, Brolin is set to reprise the role for the animated series What If? which is being produced for the Disney+ streaming service.

Thanos was originally teased in the post-credit scene from The Avengers. The scene in question sees the iconic villain turning around to face the camera, setting him up as a major threat moving forward. In the ensuing years, Thanos appeared briefly in Guardians of the Galaxy, as well as in a couple of other post-credit scenes. But he finally got his due when Infinity War hit theaters in 2018. MCU fans got to see him in action, and it didn't disappoint, as Thanos ultimately wiped out half of all life in the entire universe after gathering all of the Infinity Stones.

The Avengers managed to undo his deadly snap in Avengers: Endgame, vanquishing Thanos, seemingly for good. The movies both proved to be tremendous hits as well. Infinity War grossed more than $2 billion at the global box office, but the cliffhanger ending pushed audiences to theaters in record numbers, with Avengers: Endgame going on to become the highest-grossing movie in history with $2.8 billion worldwide. Even if we never see Thanos in the flesh again on screen, Josh Brolin unquestionably cemented his legacy in comic book movie history. Be sure to check out the video from Robert Downey Jr.'s Instagram for yourself.