I think a comic book created a continuity that they latched onto. The crossover with the furry community probably put it over the top.

This is all the fault of the Saturday morning cartoon and the comics.

There have been three Sonic cartoon series, about eight or so Sonic comic book/manga series a couple of which may still be running, at least 12 books for it, and at least 60 Sonic games of some kind or another. There's lots of Sonic media for people to get obsessed over compared to some franchises which only have a single TV series or book trilogy and pull in a decent sized rabid fanbase. I've heard the comic book series and tv shows introduced all kinds of extra characters and weird things to attract weird fans.

Also last I heard apparently everyone who writes for the comic book series now is both a furry and an obsessive Sonic fan themselves, so a large part of the official Sonic media is essentially official fanfiction.

I had the first issue of that comic as a kid. It was jammed into the back of a TMNT comic. It had Tails and a few other anthropomorphic characters in it, but it was fairly Disneyesque, talking in puns and flipping out over getting chili dogs and such, typical kids comic shit. I still can't connect the dots.

I think it started when they made Sonic Adventure 2, and decided that what Sonic needed was a complex storyline featuring a slutty bat with big tits.

Don't forget, that slutty, big-titted bat has the strength of a gymnast.

A role in a live-action Sonic fan-film is honestly the best he can do these days.

This trailer alone probably cost more than two of their movie rip-offs.

To start with, you'll need at least two consenting male partners and a length of hose.