I read the original pilot script for Stranger Things, called Montauk and HOLY SHIT things were so different!
Here's some really interesting differences I noticed:
1. The show is set in Montauk, New York, obviously, and it is a beachside town.
2. It is set on October 5, 1980.
3. The opening scene is much gorier and graphic than the final cut. More scientists die. Their skin melts off and burns. Everything is on fire.
4. Mike has a birthmark on his left cheek.
5. Lucas' last name is Conley, instead of Sinclair. He is also noted as being fairly small.
6. Dustin has glasses and is described as overweight.
7. Lucas has a crush on Nancy, and is the one to go to her door instead of Dustin.
8. The "it's a seven" interaction is not present.
9. Will asks for X-men uncanny 269
10. Joyce is from Long Island, wears a lot of makeup. She's more aggressive and demeaning towards Jonathan. She is also a waitress.
11. In general, the characters curse much more, with lots of f-bombs.
12. Mike is implied to have a crush on Jennifer Hayes (the girl who cries at Will's funeral in the final version of the show)
13. Troy and James pick only on Mike.
14. Barb has braces.
15. Steve is implied to be an alcoholic.
16. Steve invites Nancy to a bonfire at the beach.
17. Terry Ives is male, is still mentally intact and lives in Hawkins. Flo mentions that Terry called the police station talking about the Camp Hero experiments.
18. Lonnie is mentioned to be living in Philadelphia.
19. Instead of an owl attacking Eleanor Gillespie's head, it was a seagull.
20. Benny has a dog, a Rottweiler, who is also killed by the lab people.
21. Instead of fries, El eats fish.
22. Mr. Clarke is ogled by students and is apparently a very attractive teacher.
23. Benny's restaurant is called Benny's fish and fry.
24. Benny's name is Benny Henderson, instead of Hammond. (related to Dustin originally??)
25. Joyce calls Cynthia a "teenage whore" lol
26. As Mike leaves to meet Lucas, he sees Nancy sneaking out to the bonfire, instead of Steve sneaking in to study with Nancy.
27. Benny has tattoos, specifically of his exes' names. But he also has his little brother's name. Eleven somehow knows this before Benny says it. So El is implied to be able to mind-read or something.
28. Benny's death is much more graphic.
29. El injures a couple of the agents, at Benny's.
30. El takes a moment to cry when she sees Benny's dead body.
31. Nancy and Barb attend the bonfire. (Very reminiscent of the opening scene of Jaws, which is about a party of teenagers at a bonfire. In the film, a girl pulls a boy aside to skinny dip and she ends up being eaten by the shark.)
32. Steve pulls Nancy aside and SAs her.
33. Barb leaves out of frustration and is taken from her car.
34. Jonathan rides a moped!
35. Barb in the upside down is killed by a horde of demogorgans, instead of a singular one.
36. There is no rainstorm.
37. The final scene is of Joyce, Jonathan, and Hopper seeing flickering lights where they are, assumingly Barb being taken makes them flicker.