Sonic Mania’s got plenty of secrets, but this one might be its most obscure — and our favorite so far. A designer on the game confirmed that what sounds like some irritating buzzing is actually a very specific reference that only the most hardcore of Sonic fans will remember.

Last summer, a livestream celebrating Sonic the Hedgehog’s 25th birthday went about as poorly as it possibly could have. The entire show was interrupted by delays, technical difficulties and audio issues, most notably a horrific buzz that persisted throughout the show.

A level in Sonic Mania replicates that part, which a sharp-eared player picked up on. To anyone who skipped the stream last year (or successfully repressed the memory), the buzzing has no significance; but Sonic Mania designer Brad Flick confirmed that it’s a pointed reference to last year’s disastrous live event.

if you listen very closely you can hear the fucking buzzing from the sonic 25th anniversary stream. oh my god. pic.twitter.com/kcF4wgzNbD — diddy (@UnknownKongYT) August 15, 2017

“You’re welcome, Sonic fans,” Flick wrote on Twitter in response to UnknownKongYT, the user who pointed out that the sound resembled the livestream’s painful buzzing. Flick also tagged Hunter Bridges, the production engineer who publicly apologized the the event’s failings last summer.

In addition to that awful sound, there’s a sly reference to the birthday party on the test pattern in the background. Take a look at the bottom, and you’ll see the numbers “072216” — or July 22, 2016, the date of Sonic’s 25th birthday party.

Big ups to Sega for packing in such a goofy reference into Sonic Mania, which is out on consoles now.

Update: A rep for Sonic the Hedgehog gave Polygon some back story on Sonic Mania’s direct connection to the birthday livestream.

“In fact, Hunter Bridges and Brad Flick are great friends,” according to Aaron Webber, Sonic’s social media manager. “Hunter ended up becoming a project manager for Sonic Mania last year, and he worked closely with Brad to hide that easter egg in the game!”

It’s a nice conclusion to an event that still lingers in fans’ memories. We’ve updated the story above to reflect Flick and Bridges’ relationship.