How Robert Downey Jr.'s Improvised MCU Lines Forever Changed The Multiverse

In the script for Iron Man, SHIELD develops the coverup that the guy in the suit is Tony Stark's bodyguard. This is true in the original Iron Man comics, but Downey, being the real-life Stark, decided to switch things up. The MCU was forever defined by Stark declaring, "I am Iron Man." Marvel President Kevin Feige told IndieWire: 

If you're changing something for no reason, that’s one thing, but if you're changing something because you want to double-down on the spirit of who the character is? That's a change we'll make. Tony Stark not reading off the card and not sticking with the fixed story? Him just blurting out 'I am Iron Man'? That seems very much in keeping with who that character is.

In an interview for The Lost City of Z, Tom Holland spoke about the scene between Peter and Tony in the beginning of Spider-Man: Homecoming. Apparently, most of this scene was improvised. When asked, Tom said: 

I think I just tried to hug him. I just thought it would be funny if I hugged him, and Robert's instincts are so good, he was like, 'Oh, I'm not trying to hug you I'm just going to get the door.

"I love you 3000," was one of the best lines of dialogue to come out of Avengers: Endgame. The layers of emotional depth behind it, following the events and fallout of Endgame, really left a mark on audiences. To make things even more emotional, the screenwriters drew the inspiration directly from Downey's relationship with his own kids. When asked about the line, screenwriter Stephen McFeely told Insider:

The line went, 'I love you tons. I love you tons. And so, he says, 'I love you tons,' but his children say to him, 'I love you, 3,000.'

One of the most memorable gags in The Avengers is when Stark calls out a SHIELD employee, saying, "That man is playing Galaga! He thought we wouldn't notice, but we did."

In the DVD commentary, director Joss Whedon explains that Robert Downey Jr. improvised that line, and he thought it was so funny they added a Galaga screen on the man's computer in post-production. 

In Captain America: Civil War, audiences got a peek at Tom Holland's Spider-Man before Homecoming was released. When Tony speaks to Peter in his bedroom, Tom forgets his cue to move. Hence Tony's line, “I'm gonna sit here, so you move the leg.” A fan on Reddit commented:

This is pointed out by the directors in the audio commentary as a perfect example of what makes Downey such a fantastic actor.

When Iron Man and Thor meet up for a wild run-in in the first Avengers, Tony quips that he's there for "Shakespeare in the Park." He then asks the god of thunder quite confidently, “Doth mother know you weareth her drapes?” Director Joss Whedon revealed in the DVD commentary that he suggested the first bit earlier in the day, and the follow-up was all Robert. Whedon's also gone on to say:

There’s a reason Tony Stark makes fun of Thor, and mentions 'Shakespeare in the Park' in The Avengers. It’s great to play high drama and comedy alongside a modern story.