Marvel creator Stan Lee has already a long list of cameos in Marvel films, as well as other geek-friendly films and TV shows. It's pretty much his trademark to make these little appearances and as long as he's alive, he'll probably show up in future Marvel films again. It makes sense since it was already revealed that he's playing The Watcher. The image was shared by Redditor AgentoMarvel. Check it out: 

Check out this breakdown via Comicbook.com: 

1. Trial of the Incredible Hulk, X-men, Spider-Man, Daredevil
2.  
3. Hulk (Ang Lee version), Spider-Man 2, Fantastic Four, X-Men: The Last Stand
4.  
5. Spider-Man 2, Fantastic Four: Rise of the Silver Surfer, Ironman, Hulk (MCU version)
6.  
7. Iron man 3, Thor, Captain America, The Avengers
8.  
9. The Amazing Spider-Man, Unknown, Thor The Dark World, Captain America The Winter Soldier
10.  
11. Amazing Spider-Man 2, Guardians of the Galaxy, Avengers (Deleted Scene), Unknown
12.  
13. Unknown, Agent Carter, Daredevil, Jessica Jones
14.  
15. Deadpool, Captain America Civil War, X-Men Apocalypse, unknown
16.  
17. Big Hero Six, Unknown, The Big Bang Theory, The Simpsons
18.  
19. Luke Cage, Teaser, Daredevil Season 1, The Defenders? Unknown
20.  
21. Deadpool: No Good Deed Teaser, Doctor Strange, Guardians of the Galaxy 2, Spider-Man: Homecoming
22.  
23. Runaways, The Gifted, Mallrats
24.  
25. The Princess Diaries 2: Royal Engagement, Unknown, Unknown, The Avengers: Age of Ultron

Here's a video montage of Stan Lee's cameos by SuperHeroesEvolution: 

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