The first time my friend showed me Sonic The Hedgehog on his Sega Genesis, he made me put the controller down so I could see how much more attitude Sonic had than my Mario. Sonic, you see, would get pissed if you left him idling.
He was no goofy plumber. He'd tap his toe. He was annoyed.
Since then, Sonic's idle animations have been a trademark, if not a constant in Sonic games. In Sonic Generations, the upcoming hedgehog game, they're back. But there are two Sonics in this game, Classic Sonic from the Genesis era and Modern Sonic from the Dreamcast and beyond. They react a little differently if you leave your controller still.
The round one still has more of an attitude.