I'm pretty sure it's Charlie specifically. But I will now always call it the sonic cloud because that's funnierI believe that is a cloud from the 1.4.3 update, it's one of the don't starve together characters
It looks more like Super Sonic than his standard form:It looks very different from Sonic, though with the Big Eyes and Smile, and the Spiky Hair, I can see where you are coming from...
However, the art style is pretty clearly the same as Don't Starve, with the exaggerated hair style and face... So it's probably Charlie, yeah...