The Marvel Cinematic Universe has gone from strength to strength over the years, and is now one of the most lucrative movie franchises in the world.
With every film that hits the ranks, fans are introduced to a whole host of beloved new characters made famous by the comic books.
There's Chris Evans as the distinguished Captain America, Scarlett Johansson as the Avengers' leading heroine Black Widow, not to mention Chadwick Boseman's powerful portrayal of the King of Wakanda, Black Panther.
But perhaps the most beloved of them all is the one who kickstarted it all: Robert Downey Jr.'s Tony Stark, aka Iron Man.
Although fans might have been dubious when the actor was first cast as the heavy metal hero, their worries were quickly washed away when they saw him nail the role in the 2008 film.
Since then, Downey Jr.'s gone on to star as Starky in nine films, and will reprise his role in the highly anticipated Avengers: Endgame - and now the world couldn't imagine anyone else playing the iconic character.
Even the late, great Stan Lee agreed that Downey Jr. was at the top of the MCU hall of fame. When asked by a fan at the 2017 Rhode Island Comic Con who best embodied a role in the MCU, the godfather of Marvel comics (RIP) said the wisecracking genius made first place.
"That man [Robert Downey Jr.] was born to be Iron Man, you know? He'd be on the top of the list," he said.
Stan Lee putting you in first place is pretty much the highest praise you could receive as an MCU actor - and it looks like his fellow cape-wearing companions agree.
In celebration of the actor's 54th birthday this week, a number of the MCU cast and crew took to social media to pay tribute to their 'leader'.
Chris Evans wrote on Twitter: "Happy birthday to the man, the myth, the incomparable, the indomitable, @RobertDowneyJr
"You're a true original. Thank you for carrying us these last 10 years!!!"
Happy birthday to the man, the myth, the incomparable, the indomitable, @RobertDowneyJr
You're a true original. Thank you for carrying us these last 10 years!!!! :blue_heart:
- Chris Evans (@ChrisEvans) April 4, 2019
Meanwhile, Thor: Ragnarok stars Chris Hemsworth and Tessa Thompson sent him a video alongside the caption, "Happy birthday @RobertDowneyJr lots of love from all your avenger friends who are forever grateful for your awesomeness."
Meanwhile, directing duo the Russo brothers simply called him 'the man'.
Happy birthday @RobertDowneyJr lots of love from all your avenger friends who are forever grateful for your awesomeness @TessaThompson_x pic.twitter.com/npXSIhu9rQ
- Chris Hemsworth (@chrishemsworth) April 4, 2019
The love from fans poured in on Twitter too, with many citing his success as the now infamous superhero.
Happy Birthday to THE MAN. @RobertDowneyJr pic.twitter.com/tnh218WndJ
- Russo Brothers (@Russo_Brothers) April 5, 2019
His journey throughout the MCU has been one for the ages, having been cast at a time when his acting career was dwindling. Despite this, Iron Man director Jon Favreau was convinced he was the man for the job - and it's turned out to be one of the best decisions ever made by the franchise.
As Favreau once said: "It was my job as a director to show that it was the best choice creatively... and now the Marvel Universe is the biggest franchise in film history."
Happy Birthday to the one and only Starky! We can't wait to see what comes of him in the forthcoming Avengers: Endgame - 25 April, people, get it in the diary.
Featured Image Credit: Marvel