In 2019, Marvel Studios wrapped up the Infinity Saga via the Joe and Anthony Russo-directed flick. In order to emphasize the movie's importance in the MCU's history, it also functioned as the swan song to three of the original Avengers, including the franchise's inaugural hero, Tony Stark.
Tony Stark declared "I am Iron Man" just before snapping his fingers and killing the Mad Titan and his minions which referenced the ending of the original Iron Man film. Apparently, however, Downey had a string of alternatives for what's now an iconic phrase.
Initially, Tony wasn't going to say anything after getting the Infinity Stones, but that didn't sit quite well with the filmmakers when they were editing the film.
The actor opened up about this in his guest appearance on the Hypochondriactor podcast. During the episode's trivia segment, one of the questions was about Iron Man's final line in Avengers: Endgame.
"I had so many so many alt lines that I wanted to put forward...they were all super smart-ass lines like I was trying, you know, say stuff like 'you are so f*cked' or whatever... I was going to say 'oh snap!'... It was too smartass and the whole arc of the character."
He added, "It was I think maybe one of our great editor's idea or maybe one of the writers who say that we need to go back to the first film and have him his dying words to be the words of his origin. We love a bookend."