Yeah, I just got a Mastodon for unrelated reasons to Twitter's collapse (a friend I had long been out of contact with runs her own instance) so I can understand at least some of those jokes
Open-source software, anyone can start up a Mastodan site and connect to other sites (though if you don't moderate the one you're running, you're likely to get blocked by other sites)
Perhaps you'll build a gigantic pillowfort. Or collect tumblers.