Ruffalo, who was introduced as The Hulk in 2012's "Avengers," recalled his first encounter with Lee. The actor explained he was nervous about meeting the former Marvel Comics' creative leader, who passed away last November at the age of 95, because there were multiple actors who played the giant, green superhero before him.
"Playing Hulk is like my generation's Hamlet: We're all going to get a chance to do it," Ruffalo said. "So I was really nervous about 'Would I please him?' I didn't meet him until the premiere of 'The Avengers.' I walked up to him sheepishly, and he's like, 'Hey!' and he's like, 'You got it, kid!' I was like, 'Aww, that's amazing! Thank you, Mr. Lee.' Other than Downey and Kevin [Feige], I was so nervous over whether he would be happy with what I'd done."
Downey, who jumpstarted the Marvel Cinematic Universe when he first put on the Iron Man suit in 2008, shared his fondest memory of Lee -- it was during a scene for 2016's "Captain America: Civil War" where he and Don Cheadle's character Rhodey a.k.a War Machine are having a moment and Lee popped up as a FedEx guy.
"He's like all of us," Downey said of Lee. "He's a really big deal, but he's just another schmuck and we have to get his coverage in the can, too. It's like, 'And roll sound...' and he's like, [in a Bronx accent] 'I have a delivery for Tony STANK!' [Laughs] It went completely downhill after that. I was like, 'I am exactly like him.' It all goes downhill after Take One. You gotta capture it before it's gone.'"
Johansson explained she had a similar experience as Ruffalo because Emily Blunt was originally cast as Black Widow.
"I also had a similar moment as Mark when I saw him," she said. "I think it was after the 'Iron Man 2' premiere, and I was just so nervous. I didn't know how the audience or anybody would react to this beloved character and my interpretation of her, especially because I wasn't originally cast, so I also had a lot of feelings about that."
She added, "I made a career out of that! Number two! Strong number two! [Laughs] But yeah, I had a lot of feelings about it, and I saw [Lee] in the theater and he was very excited. I had a big sigh of relief after that."
Evans, on the other hand, met Lee before his time as Captain America in the MCU. If you remember, Evans played another Marvel character back in 2005 when he portrayed the role of Human Torch Johnny Storm in "Fantastic Four."
"The first time I met him was 2004, when I was doing Johnny Storm, and the day that he was on set we actually happened to have a B-roll crew," Evans recalled. "So one of my first interactions with him is all caught on video. And I found the footage! At the time, I was very early in my career, and it was the biggest role I'd ever done."
"To meet someone like him was so, so overwhelming," he continued. "He was in true Stan Lee form -- full of life and just so kind and gregarious. He just made me feel right at home."
Renner and Hemsworth voiced how Lee inspired them with his incredible sense of humor and enthusiasm.
"I aspire to be as strong-minded," Renner said. "The guy lived an amazing life. When you spent time with him, you just knew this guy was burning with the fire of life. He had a great sense of humor and a smart, smart mind. I hope and aspire to be anywhere half of what he was as a man. It's really fantastic."
"He just had a childlike wonder and enthusiasm. You'd want to talk about something like what-it-all-means and so on, and he was just like, 'No, I'm just telling stories and we're having fun!' There's a deeper meaning in the message, which he achieved so beautifully, but the childlike nature about him made me think, 'Oh, good, we can all just stay big kids forever.' He's the perfect example."