At only 19, Billie Eilish is already one of the ... So when Eilish set out to trick-or-treat for Halloween in 2019, she knew she needed a costume that could double as a disguise.

Celebrities went all-out for their Halloween costumes. Stars like Demi Lovato and Nina Dobrev have turned heads as Pennywise from "It" and Billie Eilish, respectively, while other stars like Kylie ...