Wow!
A REAL literal giant cameo! The first of it's kind? Maybe so...and the show is OK KO. Cartoon Network created a show about # , and then...for reasons unknown...Sega somehow ok'd a real, literal (speaking part!) cameo for not only Sonic, but Tails too, to appear on the show.
You can watch the clip here
(TODO = embed youtube link)
Cameos (as defined here on the pges of Gear) are Sonic stuff or images that show up in non-Sonic things, but that has never thus far extended to Sonic himself showing up somewhere irrelevent like what's happening here.
But why this?
The show is a 'just fine' place to have such a cameo happen, as it's set in some silly fake-future world where a badguy wants to take over a shopping plaza using evil robots & wacky kids/workers have to save the plaza. The Earth (or wherever) is populated by fantasy type people/characters and everyone seems to love video games & graphic novels / comics. So, it's not outlandish to have something like that happen.
But...Sega like...never does that?
Maybe this mystery will get solved, and if it does, this entry will update. But, until then, you can see IGN's official clip from the August 4th 2019 episode embedded here.
This cameo was really a doozy!
They loaded the show with as many references to things as they possibly could. Sonic & Tails were always drawn more in the 'ok ko' style so they'd fit in, but it still looked ok. Here, you can see the very specific, overly-complicated beach chair from the old Sonic OVA.
Other cameo call outs include a thing that looks like Grounder, someone does the Scratch the Chicken laugh, there's LITERALLY "Sonic Sez" from AOSTH, Sonic DOES say "And that's no good", the end-credits/weight trap scene of AOSTH is replicated, the OVA is referenced, someone steals from Knuckles, the Master Emerald appears, a Chili Dog is mentioned, 'gotta go fast' is used and probably even more. They really went to a lot of work to put in everything Sonic-fan-recognizable that they possibly could.
But that raises a very odd question which is: WHY?
Who is supposed to be watching the OK KO show? It's rated something like Y-7 which means basically babies can watch it, so ok...it's probably geared for little kids more than something like Avatar Air Bender or Steven Universe or that Original Teen Titans (NOT GO) show or something similar. But then...all the Sonic references are literally "ancient news", AOSTH was on in the 1990s....the audience for OK KO probably got born in like what? 2010 even? (They're 9)
Are any of their intended age group ferreting out old Sonic content?
Like, if you were born in 2000 and are thus 19 right now, and loved Sonic since you were born, did you go seek out the OVA, buy up all the AOSTH DVDs, and then...what? Watch up a batch of ok ko? How many people do that? Even if you don't get the references and had the games (and ignored Boom) it wouldn't stop you from thinking the cameo was fun and funny, so maybe it was just a big break out cool time for Sonic fans behind the scenes of ok ko. And if it is? That's great too. Just because not every single person will get every single reference doesn't mean you shouldn't include it. Include away!