The planet Sedna is (maybe) a trans-Neptunian planet, three times as far away from the sun as Neptune. I imagine it would be very cold there. Although it has not yet been formally recognized as a dwarf planet, it is made up of water, methane, and nitrogen ices, and has the longest known orbit of anything in the solar system. One theory suggests that its orbit is evidence for another, larger planet out past Neptune. I like to imagine a huge other planet, one that is way bigger than Jupiter - just enormous! But dark, which makes it hard to see. And it's probably teeming with life that scurries around making nitrogen iced-coffee and digging holes.
Sedna was originally named 2003 VB12, but was renamed after the Inuit goddess of the sea, who is thought to live at the bottom of the Arctic Ocean - also a very cold place. In every single version of the Sedna myth, she gets thrown into the sea and her fingers get chopped off (or fall off) as she tries to cling to the Kayak, and then she sinks the the bottom and becomes the ruler of the underworld or a mighty sea goddess or commander of the fish of the sea. Her fingers became seals and walruses and whales.
Hopefully the same thing didn't happen to the planet - being rejected by it's father, having its fingers cut off and turned into sea creatures, although one theory suggests that it was pulled into its orbit by a passing star, or captured from another star system - like Sedna was captured by the sea.
Here is what Sedna looks like to us right now:
And here is what an artist suggests Sedna might look like:
And, just to give some perspective, this is what Sedna, Inuit goddess of the sea might look like:
In conclusion, Sedna (the maybe planet) is intensely intriguing, and I hope they soon discover what exactly it is.
Photos from Wikipedia and DeviantArt.