In fact, it concerned three children who happened to be related to the directors Joe and Anthony Russo.
"The hardest [cameo to film] was a scene in the movie where it's the scene in the diner where we introduced Smart Hulk the first time," Anthony Russo explained to Cleveland.com.
"So, he's sitting there with Ant-Man, Black Widow and Captain America, and there's these three kids that walk in who are fans of Hulk. They want a picture with him.
"And those three kids are, one is my son Julian. One is my brother's daughter, Lia. One is my sister's son, Augie."
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According to the filmmaker, the production had to work between their school schedule.
Hayley Atwell recently spoke about her cameos in the film especially the one where Peggy and Steve finally get that dance.
“I thought it was a fitting end to a story that has affected so many people,” she told The Hollywood Reporter. “I thought it was very endearing, innocent and wholesome in the way that it keeps those characters in their time.
“I thought it was quite beautiful and very tasteful of Marvel to finish this 10-year story in a very simple storyline about two human beings - and one of them doesn’t even have any superpowers.
“So, I thought the tone of it, to end there, after some extraordinary things of trauma, action, effects and powers… to just have two people slow-dancing was very beautiful,” she said.
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Avengers: Endgame will soon be available on disc and DVD with several special behind-the-scenes featurettes including a special on Stan Lee.
Just because the spoiler ban is lifting, doesn’t mean you shouldn’t treat your fellow humans with respect and dignity during discourse. Or that you should run around intentionally trying to spoil the movie for people who haven’t seen it...#BeKindOutThere#NuffSaid pic.twitter.com/MMl6bpXQ4P— Russo Brothers (@Russo_Brothers) May 6, 2019
Lee, the co-founder of Marvel who sadly passed away in November 2018, appeared in every single MCU movie including Endgame and says in the featurette that he loves the cameos because “there’s no real responsibility.
Lee also says that even though he doesn’t have a favourite cameo he sad that he loves them “especially when I do one with Thor.”
Avengers: Endgame is released digitally today and physically on 2 September.