Sunshine Sorrow, the split-personality alicorn
Sunshine Sorrow is an alicorn with a strange cutie mark, it is because she tried to give herself a cutie mark as a filly and it only part worked. Normally it is a circle half black half white. When she is angry or sad it fills up black more, and if she is happy or excited it fills up white. She has only had it all black once and she can't remember the details. She likes cotton candy and flying in races.
Sunshine Sorrow also appears to have no breathing utility between her eyeballs. This is usually undeveloped due to inbreeding or intoxication of cider/inhaling smoke while the mother is pregnant with the pony. This is a terrible fact, since the pony is no longer able to create a "The two eyeballs said to eachother 'Between you and me, something smells joke. If Sunshine were to get sick, she would no longer need a breathing apperatus for her nose.
It also seems that due to this inbreeding, her head also appears to have the same skeletal structure as one of the Snorks from the classic Hanna-Barbera cartoon. It only remains an Enigma of why her nose is not there.