Stars celebrating Halloween (27 photos)

1

Derek Hough, Julianne, Fergie, Ryan Seacrest and friends

2

Pete Wentz

3

Aziz Ansari

4

Ryan Seacrest and Julianne Hough

5

Alessandra Ambrosio

6

Lauren Conrad and William Tell

7

Nicky Hilton

8

Kim Kardashian and Kanye West

9

Emma Roberts

10

Adrian Grenier

11

Fergie and Josh Duhamel

12

Christina Milian

13

Stacy Keibler

14

Ashley Tisdale and friends

15

Neil Patrick Harris

16

Diddy

17

Fergie and Julianne Hough

18

Nicole Richie

19

Josh Kelley and Katherine Heigl

20

Paris Hilton

21

Rachel Zoe and Rodger Berman

22

Hilary Duff

23

Colton Haynes

24

Alessandra Ambrosio

25

Brittany Snow

26

Jessica Alba, Cash Warren, and Honor

27

Harry Shum