To answer my own question, the alien from the "I'm Blue" video.

zorotl.com

The actual Chuck E. Cheese is said to have been a mouse named Charles Entertainment Cheese who parents were killed in a tragic accident and who made Chuck E. Cheese with his animal friends to not be lonely and bored. He even has character development, starting out as a jerk but becoming friendlier over time.

I'm sure everyone knows this by now, but I remember being surprised by how much lore is apparently in Five Nights at Freddy's when the movie came out. I had no idea that there were whole YouTube channels devoted to uncovering the lore and solving the mysteries. I always figured it was just a jump scare game for kids and streamers, and that's what it seemed like the one time I watched someone live stream themselves playing the VR version before (must have been the first game before they started all the lore stuff, I guess).

Warhammer 40k. I know it's known for having a lot of lore but even knowing that it's s shocking how much lore there is.

On Cinema at the Cinema. Tim Heidecker and Gregg Turkington have been doing this bizarre fake movie review show for over a decade now. Every year their season culminates in a live broadcast Oscar special that is a train wreck. They've also had their characters produce really shitty movies in universe that us, as the audience get to view. There are so many jokes that build up on the years of abuse each character hurls at the other. One season there was even a full mock courtroom trial where Tim was being tried for the wrongful death of 19 people that attended a music festival he put on.

Most of the early seasons are available on YouTube, and there is even a guide @ oncinematimeline.com, but the newer seasons require a subscription to view. Really worth it more than any other streaming service.

I can't recommend it enough.

In the early days of Halo I was shocked at how fleshed out the universe was. The games seemed to rush through the story without a ton of background and when playing them I always felt like I was missing some key information. I read some of the books and a Halo encyclopedia and it's really easy to get lost in the lore!

Power Rangers and Teenage mutant ninja turtles.
Holy crap.

https://www.reddit.com/r/riskofrain/comments/yeiv21/egocentrism/#lightbox

Sorry for the bad site but here's my favorite. It's a fan art made by the person who posted it.

Risk of Rain has some absolutely amazing lore. The source is from the in-game description of the item Egocentrism, hence the title.

Chris Chan.

The world from League of Legends, Runeterra, has an astonishing amount of stories across a lot of smaller side project games and a Netflix show, Arcane. Riot built a big world with a huge cast of characters. And all that writing and storytelling was for a MOBA.

The Mad Max movies, specifically the more recent ones

There's a couple of odd vids that Adult Swim has put out from Alan Resnick, like May I Enter Please? and Unedited Footage of a Bear. There's one vid that's just as weird as them called This House Has People In It, but the notable thing is this 12-minute video has a whole ARG behind it, enough to fill a video explaining the lore for over an hour and a half.