She was the result of a drunken one night stand between the two (after Moondancer decided to try out a gender-swap potion to be kinky). Shortly after this, Strawberry found out that she was pregnant, and this caused both of them to freak out.
After calming down and having some thought into it, Moondancer said that she would look after the baby by herself and would be it’s mother, with Strawberry agreeing.
Later on when Moondancer falls in love with and marries my oc Nocturne Scroll (more on her later), Moonberry would officially become part of her family.
Strawberry was pregnant before she and AJ started dating, but she made sure to tell Aj about this early on in their relationship. Applejack was ok with this and was supportive of Moonberry, and Moonberry see’s Strawberry as a step-mother, and Applejack ad her family as cousins.
As for Moonberry herself, she has an interest in science and magic. She likes to learn about new thinks and is very eager to learn about new subjects.
She also likes a lot of fruity things, such as smells and tastes.