Robert Downey Jr. Celebrates His Birthday Like A King; Chris Hemsworth Calls Him 'Special Human'

Robert Downey Jr. turned 56 on Sunday and he celebrated it like a king! The "Iron Man" actor took to Instagram on his birthday to share a picture of him standing in front of a big balloon that read "56."

In the photo, the actor could be seen standing in front of a glass window showing the peace sign, with small blue and white balloons in the background. The actor also donned a king's crown on his head along with a maroon suit. He completed the look with a pair of sunglasses.

"Much love and gratitude for all of the birthday well wishes! Many reasons to feel blessed today. #HappyEaster #HappyPassover #BirthdayDowneyJr," he captioned.

His co-star Chris Hemsworth posted a sweet tribute for the actor.

"Happy birthday to this very special human! Thanks to his mind blowing creativity and unrivalled leadership we were all able to ride on his coattails through the marvel cinematic universe forever grateful," he captioned. "Love ya mate @robertdowneyjr."

Other celebs also wished Downey Jr. on his birthday. "Avengers" co-star Mark Ruffalo, who portrayed "Hulk" in the superhero franchise, took to Instagram on Saturday night and wrote, "Wishing my other half of the #ScienceBros a happy birthday! @robertdowneyjr."

Jeremy Renner, who portrayed Clint Barton in the film series, also wished the "Sherlock Holmes" star.

"Happy birthday to my dear friend @robertdowneyjr Happy Easter to you," he captioned. "Bestowing loads of love and laughter with family and friends today my brother."

In an interview with Fast Company last year, Downey Jr. shared his future plans about the "Sherlock Holmes" franchise.

"At this point, we really feel that there is not a mystery-verse built out anywhere, and Conan Doyle is the definitive voice in that arena, I think, to this day," he said. "So to me, why do a third movie if you’re not going to be able to spin off into some real gems of diversity and other times and elements?"

Downey Jr.'s upcoming project includes "Black Widow" and his highly anticipated mystery thriller, "Sherlock Holmes 3," which is all set to release in December this year.