Happy Halloween! The main event happened yesterday, but many stars got a head start on the fun over the weekend. We've seen lots of celebrity Halloween costumes from various parties and events, and the A-listers were also happy to share some of their own snaps online. We've collected photos from Brooklyn Decker, Nina Dobrev, Zac Efron, Jessica Alba, and many more — click through to see the images shared on Twitter!
See All the Celeb Halloween Costume Pictures From Twitter!