Robert Downey Jr. has worked with so many A-list actors and actresses over the years because he has been in such a long list of top-notch movies. His career spans back decades and some of the awards he has won include the BAFTA Award for Best Actor in a Leading Role and the Golden Globe Award for Best Actor Motion Picture Musical or Comedy.

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The stars who have been lucky enough to work with him for various roles usually have nothing but amazing compliments to say about Robert Downey Jr.! After reading these quotes, it's clear that Downey is one of the most amazing costars to work with.

10 Mark Ruffalo

Mark Ruffalo was hesitant to take on the role of the Hulk... until Robert Downey Jr. gave him a shove in the right direction. Mark Ruffalo revealed, "I got a call from Downey-- it must’ve made it to him that I was hemming and hawing-- and he just simply said, ‘Ruffalo, let’s go. We got this.’ In true Iron Man fashion. And then after that, I was like, ‘I guess I have to do it.'"

By hemming and hawing, Mark meant that he was going back and forth about whether or not to accept the part. It is a good thing Robert stepped in and convinced him to make it happen.

9 Juliette Lewis

Natural Born Killers and Due Date are the two movies that Robert Downey Jr. starred in alongside Juliette Lewis. She actually really enjoyed her time working with him on the sets of the movies. She talked about her experience saying, "[It's] just the best. I remember being in the rehearsals, all of these things just came on the fly, like his Australian accent... It was like there was no creative impulse he wouldn’t take. It was really fun. But Downey is just an improv wizard. He’s electric and he was just phenomenal as this bizarre Wayne Gale character."

He is great when it comes to improvisation and he has even helped another famous actress with that very task-- more on that coming up!

8 Gwyneth Paltrow

Gwyneth Paltrow played Robert Downey Jr.'s love interest across the board in several Marvel movies. He was Iron Man, she was Pepper Potts-- one of the most iconic comic book couples ever. She talked about what it was like working with him saying, "I get to do a bit of action and I get to wear the Iron Man suit for a while - it's very cool. It's quite cumbersome but not so bad. I thought it was going to be terrible because in the first two movies Robert would put on the suit and start sweating, he'd have a nervous breakdown and would meditate and cry. He was in hell. So, I was like, 'Wow, I'd better start mentally preparing myself for the suit,' and I put it on and was like, 'This guy is a wimp, it's really not that bad.'"

The suit obviously wasn't as bad for her as it might have been for him since they've had such vastly different experiences.

7 Michelle Monaghan

Michelle Monaghan worked with Robert Downey Jr. in the movie Kiss Kiss Bang Bang. They also worked together in the movie Due Date, although they didn’t really share too much screen time in that movie since the entire film consisted of him taking part in a wild road trip to get back in time before his wife went into labor.

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According to Vanity Fair, Michelle revealed that he taught her a thing or two about improvisation and acting and helped her feel a lot less nervous about things in front of the camera.

6 Rachel McAdams

One of the newest Sherlock Holmes movies starred Robert Downey Jr. alongside Rachel McAdams. He played the titular role of Sherlock while she played the role of Irene Adler. She enjoyed working with Robert!

She said, “He paved the way to how much the audience was craving fully-formed, fully-fledged human beings. They’ve become really rich worlds.” He truly did do an excellent job in the movie!

5 Brie Larson

The biggest movie franchise ever -- the Marvel movie franchise -- obviously stars Robert Downey Jr. in the role of Iron Man. Brie Larson took on the role of Captain Marvel starting in 2019. The two actors linked up for Avengers: Infinity War in 2018 and Avengers: Endgame in 2019.

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After Robert Downey Jr. hosted a cute lunch for Brie Larson and the rest of the female cast, she tweeted, "Remembering when @RobertDowneyJr hosted a 'Women of Marvel' lunch for us. We powerful. We cute. Thanks @zoesaldana for the photo." He spoiled his female costars with a meal to show them how much he appreciated them all.

4 Jude Law

Sherlock Holmes is the movie that Jude Law starred in with Robert Downey Jr., but they discussed joining forces for Marvel films quite a bit, too.

Jude Law revealed, "I don't know that he ever gave me any advice, but... He talked a little bit about how [making a Marvel movie is like] fitting this one piece into a bigger picture that someone else has got their eyes on, and giving yourself over to that. It's not about trying to understand everything. Just do your piece." Jude Law ended up playing the role of Yon-Rogg in Captain Marvel, so he obviously took the advice!

3 Jessie Buckley

Jessie Buckley worked with Robert Downey Jr. on the movie Dolittle. She had a great time working with him. When asked about working with him on set she revealed, "It's so much fun, it's really playful! He's incredibly playful. It's amazing to watch his imagination it's just something that's so unconscious yet also like an exorcism."

Dolittle is a great comedy film to watch about a doctor who can talk to animals. It is a remake of the Eddie Murphy version from the late 90s.

2 Scarlett Johansson

Just like Brie Larson, Scarlett Johansson worked with Robert Downey Jr. in several Marvel movies. They are good friends with each other behind the scenes, too! During an interview with ScreenSlam, she explained, "I've never been a part of something this big. For me, it was really just the opportunity to work with Jon [Favreau] and work with Robert [Downey Jr.] and work with Gwyneth [Paltrow]..." She is just as important to the cast as the famous names she listed.

1 Zoe Saldana

During an interview on Jimmy Kimmel Live, Zoe Saldana talked about her amazingly incredible experience filming Avengers: Infinity War with her superstar castmates. She said, "[It was] one of those shooting times I was so sick and where people were just afraid to come over and say hello. I was just a pathetic green thing on set. There was a knock on my trailer and it was Robert's assistant dropping off a whole bunch of supplements that he had put together for me as a get well little package."

He sent over something he thought would help her feel better quickly, which just goes to show how thoughtful of a guy he really is!

NEXT: Here's Why DC Fans Don't Like Robert Downey Jr.