Meet Ind, Ivi, and Si, the Cerberus pony :3
 
3 mares, who are all part of a single body, with each one of them constantly switching between control of the dominant personality for it.
 
Ind is the more shy and introverted of the 3. She keeps feeling like everyone thinks that she is a freak, and keeps looking on the negative side of things, acting like a downer to a lot of ponies.
 
Ivi is the more balanced of the 3 personalities. She likes to take things cautiously and wants to think things through before taking action on anything. Often the voice of reason among the group.
 
Si is the more smug and hot headed of the 3. Often likes to cause trouble and can act very smug most of the time, and enjoys scaring others due to her appearance. Often ends up getting the rest of the group into trouble.
 
Despite their differences, all 3 of them love and support each other dearly.  
All 3 of them are bisexual (Ind is more into stallions, Ivi is into both mares and stallions equally, and Si is more into mares)