Meet Moon Pie.

The two headed fusion of Princess Luna and Pinkie Pie from an alternate reality.

In this universe, Luna was an evil queen who was slain by her own subjects and Pinkie Pie who was just a mere warrior typically sent out alone to scout and hunt for food. Pinkie found Luna's remains and Luna offered her great power and "eternal" life if she finds her the one and only perfect candidate to serve as her new body.

the one and only perfect candidate to serve as her new body. However, Luna possesses Pinkie as she granted him power to complete the task. That didn't turn out well as Luna's arrogance lead to forever losing the candidate. Years later being stuck with each other Luna's spirit began to manifest a physical form within Pinkie's body. Because of this the two are forever bound to each other, but it's not all bad cause Pinkie got all the things she was promised anyway and has dominant control of her body. she does allow Luna to use her right leg until she needs it.