1. In It Chapter Two, Michael looks through a scrapbook that contains a local newspaper article about the fire that killed his parents. The fire spells "IT."
2. When the characters try to reprogram Buzz Lightyear in Toy Story 3, you see that his batteries were manufactured by "B N L," which stands for "Buy N Large." This is the same company shown throughout Wall-E.
3. It is a running gag in Fantastic Mr. Fox that instead of swearing, the characters say the word "Cuss." One of the buildings in the background actually has the word "CUSS" spray-painted as graffiti.
4. In Indiana Jones and the Last Crusade it is revealed that — when he first uses his iconic whip — Indiana nicks his chin, giving a story to the prominent scar (because, ya know, Harrison Ford actually has that scar IRL).
6. The rubble of the destroyed Asgardian mural in Thor: Ragnarok outright foreshadows the injury he receives later.
7. During the awkward Thanksgiving scene in Spider-Man, Peter Parker is wearing the Green Goblin's color scheme, while Norman Osborne is wearing Spider-Man's.
8. In The Santa Clause, there are several elves hidden in plain sight throughout the film to show that they're keeping an eye on Scott and Charlie over the course of the year before they return to the North Pole.
9. When Forrest is at Jenny's bedside in Forrest Gump, you can see a smiley face greeting card on the dresser — the same smiley face design he helped "inspire" earlier in the film.
10. The outfits of Nakia, T'Challa, and Okyoe during the casino scene in Black Panther were specifically chosen to represent the Pan-African flag.
11. In Blade Runner 2049, it is stated that replicants can be revealed by having them "look up and to the left." In the opening of the film, the first word you see is the word "REPLICANTS" in the upper left-hand corner of the screen.
12. In Sully's apartment in Monster's Inc., his armchair has a big ol' hole in the back for his tail to comfortably fit through when he's sitting down.
13. After Boromir dies in The Lord of the Rings: The Fellowship of the Ring, Aragorn puts on his bracers to honor him. Aragorn can be seen wearing them for the remainder of the films.
14. While Arthur is practicing for his interview in Joker, he has set up his entire living room to look like the set of The Murray Franklin Show, even down to having scribbled "Murray Franklin" on his mug.
15. Speaking of the Joker — the factory that Charlie's father works for in Tim Burton's Charlie and the Chocolate Factory makes "Smilex" toothpaste. "Smylex" is the same name as the poisonous gas created by the Joker in Burton's Batman.
16. After Lilo and Nani adopt Stitch in Lilo & Stitch, they walk by a Chinese restaurant named "Mulan Wok."
17. And finally, in Harry Potter and the Prisoner of Azkaban you can see Buckbeak poop* right before he walks up to greet Harry for the first time. IDK, it just made me giggle. Here ya go:
View this video on YouTube
*Right around the 43-second mark.