Your Hatterene was a loyal one, always by your side whether in battle or just with you and themself. That meant they matched outfits with you and were able to walk around with you around certain public places without it having a breakdown. So when it saw a shop that would sell human AND Pokémon matching outfits without you having to make them!

And since you couldn’t say no, you both were wearing the same outfit and the both of you were ten times happier!