homestuck is a webcomic that grew out of a forum game where someone would draw a starting panel, someone would suggest the next thing that happens, and if the artist liked it they would draw that panel. andrew hussie already did this once with a detective style comic called problem sluth, that grew increasingly out of control into like, magic and space monsters and shit. homestuck started out as the same idea but about cartoon teenagers who have to solve adventure game puzzles to figure out the mystery of what happened to their world and stuff.

hussie eventually stopped taking suggestions and just wrote what he liked, which became increasingly convoluted. you basically can't follow it without checking the wiki over and over. he kept the spirit of audience participation by basically building a little group of fans who would produce work for him to put into the comic (one of these people is toby fox). this eventually ended up with dozens of people working on this increasingly profitable comic enterprise for free, and gave hussie a big ego that resulted in a lot of pretty big issues when he tried to develop games based on the concept, like a ton of miscommunication and delays and thrown out work etc.

but yeah the thing that attracted people to homestuck is that it's about teenagers talking to their friends online about silly crap, which meant teenagers who talked to their friends online about silly crap would talk about homestuck, and make homestuck fan stuff, and then eventually work on official homestuck stuff. it created its own little world and it sucks that it's kind of been in limbo because the creator couldn't manage the beast he created