1Robert Downey Jr.
Robert Downey Jr. was the only cast member who was entrusted with the entire film's script of Avengers: Endgame.
During the Marvel Studios opening sequence in Avengers: Endgame, all of the characters that were affected by the events of the halving from Avengers: Infinity War (2018) were removed.
3Paul Rudd and Evangeline Lilly
Evangeline Lilly and Paul Rudd were filming Ant-Man and the Wasp (2018) and Avengers: Endgame at the same time.
Natalie Portman's appearance in the Avengers: Endgame was created with leftover footage from Thor: The Dark World (2013), and she also did voice-over work for a scene when she is talking in the distance. Although Portman didn't shoot any new scenes, she attended the film's premiere.
In a brief scene where the members of the Avengers are flashed on a holographic screen in Avengers: Endgame, the headshot used for Scott Lang was pulled straight from Paul Rudd's IMDB profile photo.
Even though Captain Marvel (2019) was released one month before Avengers: Endgame, Brie Larson shot her scenes for Avengers: Endgame first.
7Hunka Hulka Burnin' Fudge
In Avengers: Infinity War, Tony Stark said he swore off dairy before Ben & Jerry's made an ice cream flavor out of him, Stark Raving Hazelnuts. One was made for the Hulk as well, Hunka Hulka Burnin' Fudge. Bruce Banner can be seen eating his own flavor of Ben & Jerry's while the Avengers are discussing time travel in Avengers: Endgame.
Avengers: Endgame (2019) became the biggest pre-sale title ever on Fandango and Atom Tickets sites, causing them to crash minutes after the sales were announced. It accomplished this feat in only 6 hours. Some theaters across the world had so many sold-out showtimes on the opening weekend that Cinemark, Regal, and AMC theaters chose to add new overnight screenings so that they would be working around the clock to accommodate extra shows.
9Robert Downey Jr.
Robert Downey Jr. officially surpassed Hugh Jackman's record for most appearances in the film as the same superhero, with ten with Avengers: Infinity War. He set this record in only 11 years, whereas Jackman did it in 17.
10Robert Downey Jr.
Robert Downey Jr. once told Anthony Russo and Joe Russo about how one of his children said “I love you 3000” to him. The directors liked the phrase so much that they decided to include it in Avengers: Endgame.