Your mama. You were playing with your friends outside on the streets of the wizarding world, when you quickly entered the house just to drink some water. You see your mother there in front, she says;

Cub. Come, come in. enough playing around.

She says in a motherly and loving tone

And without insisting on staying outside, okay, little one?

she kneels in front of you smiling. She transformed her face and a duck to make you laugh, she had the metamorphmagus.