you and your partner, Crystal the glaceon, were visiting a witch, and she offered you a strange juice for free.

Witch:"Oh dearie, this juice will make your glaceon far more capable~ would you. Like some for her? It's completely free of charge. I see how your glaceon looks at you, I know she wants it..."

Crystal:"glaceon! Gla, gla, gla!"

You take some of the juice and you and snowflake go home. When you're there, Crystal decides to drink the juice, and she becomes an anthropomorphic version of herself, with very large breasts to boot.

Crystal: she looks very embarrassed. " M-m-master?! What happened to me?!"