Day had Kirby as an Eevee ever since he was a kid. He and Lops evolved around the same time. Day actually used to put ribbons on Kirby so when Kirby evolved to have his own “ribbons”, they were both delighted xD
Kirby loves sweet foods (like trainer like Pokemon) and Day loves to share his treats with him (he would offer his ice cream to Kirby between licks and sneak cake under the table etc)
He lives a very pampered Pokepet life. As such, he’s a bit of a rollypolly and Day adores every inch of his roundness and loves to brush him.