The stamp of a Marvel movie is the inclusion of Marvel Comics mastermind Stan Lee. Whether he's driving a bus, riding one, or standing where they pass by waiting to explain how one person can make difference -- the comics icon often offers memorable moments in movies based on characters he had a hand in creating. Prior to passing away in 2018, Lee had filmed several cameos for upcoming films. However, Avengers: Endgame looks like it will be the last.

Speaking to ComicBook.com at a press event for Avengers: Endgame, co-directors Anthony Russo and Joe Russo were asked about Lee's cameo in the upcoming film.

"This was his final cameo that was committed to film," Joe Russo said, as seen in the full interview video above. "It was always... Again, I grew up as a Marvel fanatic, and watching Spider-Man cartoon show as a kid with his voice in it. I think anything that affects you as a child really affects you as an adult, sticks with you. So when he would come on set, and we'd hear his voice, it's sort of Pavlovian in a way, where you just become a child again. The whole crew would be like that. People were always... All these movie stars on set every day, and then Stan would show up, and it was just like people were kids all over again."

Of course, the details of Lee's final cameo in the Marvel Cinematic Universe are being kept a secret as is much of Avengers: Endgame. He most recently appeared in Captain Marvel, being seen in 1995 riding a train to the set of Mallrats and rehearsing his lines from that unforgettable cameo on the way.

In fact, there is no way fans could possibly predict Lee's cameo or the outcome of Avengers: Endgame, according to the directing duo.

"We spend months and months and months thinking about all the possibilities," Anthony Russo said. "So there are a lot of ideas that we run down that are nothing like what the movie ends up being. It's just part of the process. There's so many different places you can go with a narrative, that sometimes some of them get somewhat close, but nothing is ever exactly what the movie is, just because there is a level of detail in the movie that goes way beyond. Most theories you read online, they take three or four sentences to convey. The movie is a very dense document."

What do you hope to see in Stan Lee's final cameo within the Marvel Cinematic Universe? Share your thoughts and enthusiasm in the comment section or send them my way on social media, @BrandonDavisBD.

Avengers: Endgame hits theaters on April 26.