What in the HELL is this all about?! I have never, ever heard about this, but apparently it's the real deal. At one point in Sonic's history, the blue blur apparently had an ability that would make him sneeze to alert him to danger. Similar to Spider-Man's Spider-Sense, but much weirder.
There's all sorts of history to this sneeze ability as well. It's even part of the Sonic CD intro animation, albeit a very quick portion. There's official Sonic comics and promo materials that mention the sneeze, and even a cut sneezing sprite animation from Sonic CD itself. Man, you think you know everything about a character, and then something like this is unearthed!