I Love You 3,000
Avengers: Endgame was the end of an era. It tied up the events of 11 years’ worth of films in just 181 minutes, so it was easy for people to miss a few tiny details. There was one easter egg that wasn’t provided by the scriptwriters or the comics but rather RDJ himself.
Near the end of the movie when he wishes his daughter goodnight, he tells Morgan, “Love you tons,” to which she replies “I love you 3,000.” This is an actual saying that Tony uses with his kids, and the Russo brothers loved it so much that they decided to add it to the script.