Kingdom of Loathing is an incredibly long-running browser-based MMO that started way back in 2003. I was indirectly introduced to it through Homestar Runner, which KoL sometimes pays homage to in its various items, enemies, and sidequests, though I never made an account there because my closed teenage mind didn’t care about any browser-based MMO that wasn’t Neopets. For as far as I can tell, KoL is still running to this day, even after 14 years, and unlike Neopets, there has been no black void in announcements, updates, and community events.
If you don’t quite have the money for West of Loathing but want to experience all of the humor, then now’s a good time to sign up for Kingdom of Loathing. It’s free. They do keep their site running through donations, and there’s a monthly reward for donating at least 10$ in that month.