Mark Ruffalo Calls Robert Downey Jr. 'Science Brother For Life' On His Birthday

Mark Ruffalo's birthday tribute to Robert Downey Jr. is rather special. Ruffalo shared a GIF featuring the two of them in an Instagram post and called the "Iron Man" star, who turned 57 Monday, his "science brother for life."

In the GIF, which was apparently from when they were promoting the 2015 Marvel movie "Avengers: Age of Ultron," both actors can be seen laughing.

"Wishing a happy birthday to my science brother for life, @robertdowneyjr!" Ruffalo captioned the post. "Hope you enjoy your day Old Pal!"

Fans took to the comments section to share their reactions to the post and wish Downey Jr. a happy birthday.

"Happy Birthday RDJ! Science Bros love is so pure!" one of the fans wrote, while another fan commented, "I want to see old friends together again."

"Happy birthday to him, you both are awesome. I hope you work together again," another user noted.

Ruffalo first played Hulk in the 2012 flick "The Avengers." Hulk's character was first introduced in the 1962 comic book "The Incredible Hulk #1" by Stan Lee and Jack Kirby.

Downey Jr., who portrayed Iron Man in the Marvel movies, first appeared in the 2008 movie of the same title. Iron Man's character was first introduced in "Tales of Suspense no. 39" comic book, which was released in 1963.

Ruffalo will be next seen in the Marvel TV series "She-Hulk," which is currently under post-production. The show will be released on Disney+ this year.

He will also appear in movies like "Poor Things" and "Newsflash." The actor is currently filming the miniseries "All the Light We Cannot See." He was recently seen in the Netflix movie "The Adam Project," alongside Ryan Reynolds and Jennifer Garner.

Downey Jr., on the other hand, last appeared in the Marvel movie "Avengers: Endgame," which came out in 2019. The movie marked the death of Iron Man's character, which means the actor might not appear in future Marvel movies. The actor also featured in the fantasy adventure movie "Dolittle," which was released in January 2020.

Fans can see him next in movies like "All-Star Weekend," "Oppenheimer," "Sherlock Holmes 3" and "Play Dirty."