'Avengers: Endgame' is Stan Lee's final Marvel cameo

Brace yourselves, true believers. Avengers: Endgame will be Stan Lee's final Marvel Cinematic Universe appearance.

"It’s his last one committed to film," director Joe Russo confirmed to Mashable at a press day in Los Angeles. (Previously, he had said he was not sure if Lee had shot one for the upcoming Spider-Man: Far From Home.)

While the Russos didn't say what, exactly, Lee's cameo would be in the movie, they were happy to reminisce about their time with the comics legend.

Anthony Russo, a self-described "comic book nerd" as a kid, recalls how was "weird" when Lee would come to set -- in a good way.

"We have all these movie stars on that set, and when Stan came to set, everybody would be like kids again," he said. "It was always a lot of fun shooting these cameos because he was very charming, and he would maybe get the crew going, and everybody would be laughing and having a good time."

Although Lee's passing is undoubtedly tragic -- and although any Marvel fan is sure to feel a little bit heartbroken seeing his face onscreen one last time -- Endgame does seem like a fitting end.

"I have to say, I think it’s astonishing that this would be his last cameo," remarked Joe. "It’s just kind of mind-boggling that he made it to the end of this run. I can’t believe it."