Nibiru is a special planet. The reason? Because it's imaginary. It's an imaginary planet that is supposed to collide with Earth in, oh, give or take two months (December 12, 2012). This sneaky planet has decided to do a flyby of Earth, causing us to stop orbiting for five days and switch magnetic poles. The oceans would then migrate to the poles, creating two polar oceans and one giant center continent. And a day would be the length of an entire year - unless of course the planet started spinning again after five days, in which case the oceans would wander back to their original locations and Daylight savings time would be pushed back a few days.
Nibiru is a hoax. But Nibiru would make a great science fiction TV series, if anyone is interested. Maybe I'll write a book - Incoming Planet. Watch your nearest amazon.com.
As for what Nibiru looks like, I did a simple image search It's quite lovely. It looks like a marble:
And it comes from a really reliable-looking website.
This one is a "real photo" from NASA, found on ufodigest.com.
And if you're still dying for evidence, check out this one. You can't deny that this is a real picture:
For more information on this impending disaster, you can read this article, the Wikipedia page, or the news.
In conclusion, Nibiru is going to be great fun.