Just a Baseball furry

Seam is an old plush toy. This kind of toys is usually made for children and becomes "obsolete" as soon as a child grows up. But Pink is something so special and magical - she is a literal embodiment of a deep connection between toy and its owner. This doll will never be abondened like Seam was. And unlike lightners of card kingdom who "abondened" their darkners (yes I know that gerson died, but please entertain the idea for a moment) Pink wants to build meaningful relationships with darkners, wants to be one of them.

Plus she is also a CAT MAGICIAN, who Seam can train to become a worthy opponent for them in the games this old cat used to play with jevil. There even is a dialogue that can be a hint at their future interaction