You can change the look of villagers using a Birthday Cake.
However, you can not change the villagers living in collecter's item houses.
Hat & hairstyle[]
Only villagers of same color as house ( Wood Cottage, Small Cottage, & Small House Villagers )
There is a different style by a body color. There is also a fixing style of boys and girls.
Wear[]
Glasses & shoes[]
Birthday and if used the birthday cake, sometimes shoes or glasses options appears.
Glasses
Shoes