Writing about printable masks for Mardi Gras, I was particularly taken with the fierce dragon masks. I suspect children may be too. Masks both terrify and delight children, even the non-frightening ones. My oldest was petrified of clowns and costumed people as an infant (long before clown fear was a thing).
Why? Because a child's sense of object permanence is not fully developed. They don't realize that things hidden still remain. Even people. Children think people change when they put on costumes, that they become that thing or person. Imagination, Dress Up, Pretending are Crucial to Child Development