1 of 38
JENNIFER LOPEZ & CASPER SMART
How about a little peace and J. Love? Lopez and her beau don't let a little thing like being on a world tour stop them from celebrating Halloween, rocking some serious flower power all the way from Oberhausen, Germany.
2 of 38
"Every cloud has a smoky gray lining," as Jane Lane would say, and Perry looks the part, accompanied by Daria, played by real-life best friend Shannon Woodward, at a Los Angeles party.
3 of 38
4 of 38
5 of 38
6 of 38
If anyone could convincingly play the Hulk, it's Dwayne Johnson, who Tweets a warning: "Don't make angry. You wouldn't like me when I'm angry."
7 of 38
To infinity ... and beyond! Bullock keeps her hat on as Toy Story 2's Jessie, while son Louis, who turns 3 in January, has her back as Buzz Lightyear.
8 of 38
Sea horse crossing! Hannigan, husband Alexis Denisof and their two little girls, 3½-year-old Satyana and 4-month-old Keeva, go trick-or-treating in their L.A. neighborhood as one big, glittery family.
9 of 38
10 of 38
Sandy makes an appearance on the West Coast thanks to Rimes, who snuggles up to her Danny, husband Eddie Cibrian.
11 of 38
CALISTA FLOCKHART & HARRISON FORD
The couple that dresses up together, stays together? For a night out in L.A., Ford and Flockhart coordinate frumpily as Betsy and Timmy.
12 of 38
"Anchors away!" Tweets Lavigne, who ships out for Halloween as a saucy sailor.
13 of 38
Forget 40 is the new 30 – 40 is the new sexy for McCarthy, who celebrates her milestone birthday with a purr in Las Vegas.
14 of 38
The 15-year-old actress goes to town in her witchy getup, enjoying Halloween in London at Ross's star-studded event.
15 of 38
Soldier Osbourne gets freaky when he puts on wife Lisa's blue wig.
16 of 38
Let them eat cake! Messing puts on a towering wig for Bette Midler's annual Halloween party in New York.
17 of 38
18 of 38
19 of 38
20 of 38
For a spooky tumble down the rabbit hole, the hosts of The Talk went all-out. Sara Gilbert played Alice, Julie Chen was the Mad Hatter, Sharon Osbourne was none other than the Queen of Hearts, Aisha Tyler was the Cheshire Cat and Sheryl Underwood rounded out the group as the White Rabbit.
21 of 38
Elmo loves Mark! The Dancing With the Stars pro brings some Sesame to Elm Street at a party in Hollywood.
22 of 38
23 of 38
24 of 38
Channeling old-school Cher, the talk show host tapes a Halloween-themed episode of The Ricki Lake Show surrounded by audience members in costume.
25 of 38
Scout's honor! Glee star Darren Criss looks ready for an expedition in the woods at costar Matthew Morrison's Halloween party in West Hollywood.
26 of 38
27 of 38
She's ready to seduce with her eyes! Keibler shows off the intricate mask she wore to host a Sin City masquerade party.
28 of 38
Time for some Purple Rain? Diddy gets sexy as Prince for Hugh Hefner's Halloween party in Los Angeles.
29 of 38
30 of 38
Halloween is so Monster High. For Matthew Morrison's party in Hollywood, the 90210 star shows up looking like Frankie Stein from head to toe, thanks to a costume designed by Project Runway alum Chris March.
31 of 38
CHRIS COLFER & ASHLEY FINK
Also at Morrison's party, Glee costars Colfer and Fink conspire as a llama assassin (complete with brass knuckle hooves) and a bunch of grapes, respectively. "You know its a good Halloween party when even the farm animals are grabbing yo' grapes!" Fink Tweeted.
32 of 38
From DWTS pro to Jedi master! Hough has Yoda on his back and a lightsaber in his hand for a party in Beverly Hills.
33 of 38
Who's the Queen of Hearts? The singer goes for a touch of Alice in Wonderland (without the anger-management issues) at Morrison's Halloween party in Hollywood.
34 of 38
It's Hotter Than Hell in this kitchen! The country singer and Food Network star (third from left) gets surprised by husband Garth Brooks (not pictured) and their daughters, August (far left) and Allie Brooks (second from left), who helped their mom get into character as rock band KISS.
35 of 38
NEIL PATRICK HARRIS
An ab-tastic Harris cries vampire tears when he and partner David Burtka (not pictured) step out for a frightful night in Hollywood.
36 of 38
37 of 38
The queen's got her knight in shining armor! Christina Aguilera poses with boyfriend Matthew Rutler outsider her Beverly Hills home.
38 of 38
World’s Most Beautiful: See Who Else Made the 2017 List!
The Bachelors of Seasons Past: Where Are They Now?
The Most Adorable Things Chris Pratt Has Said About Marriage and Fatherhood
Meet the Stars Bringing Your Childhood Dreams to Life as Live Action Disney Characters