you catch a Sylveon, but this Sylveon was special, it had the ability to talk, and to define their master, so one day when you decided to try to wear something pink your Sylveon comes out and decided to have fun with you by putting you in diapers and making you look like a baby girl

Sylveon: comes out your Poke’Ball Oh? So you like wearing pink? Well if that’s the case why don’t I turn you into my baby girl so you can enjoy pink more~