Something funny's going on with the Sun that astronomers can't quite figure out.
No, it's really, really round. As the article notes, if you shrank the Sun to the size of a beach ball, the difference between its widest and its narrowest diameters would be less than a human hair. And it should be less round because it's not solid, it's made up of gas.
When solid things spin around on an axis, they may bulge a little here or flatten a little there if they spin fast enough. But because they're solid, that bulge is minimal unless they're spinning very fast on their axes. This lends some credence to the theory that the reason Earth is between Venus and Mars is because Venus asked Mars if this particular revolving velocity made her look fat and Mars took just a leeeetle too long to answer.
Anyway, when masses of gas spin on their respective axes, they don't have the solidity to stay round and they flatten out much more easily than do solid objects. The Sun us just such a mass o' gas. If you could somehow survive the heat and radiation, you could fly straight through the thing. Given that the Sun spins on its axis once every 28 days, astronomers have a rough idea about how much flattening should be going on, and it isn't.
Right now they chalk it up to the fact that they can't really see what's underneath the photosphere, or surface layer of the Sun, and have only theories about how the gas below that layer is acting. Some possibilities are solar turbulence or some kind of magnetic interaction, but right now there's no solid answer as to how the Sun keeps its near-perfect figure.
Rumors that it's from skipping sweets between meals and doing some wicked hard P90X have not, as yet, been confirmed.