Alyson Hannigan and her husband Alexis Denisof took their adorable daughters Satyana and Keeva trick or treating in Brentwood yesterday, and the whole family dressed up as adorable seahorses!

The How I Met Your Mother star tweeted, "Gotta go get some glitter makeup for tonight!!!!" before they combed the neighborhood for candy.

Miss Hannigan clearly relishes in motherhood! We wonder if she's giving her HIMYM co-star Jason Segel any tips on helping parent his girlfriend Michelle William's daughter Matilda?

In other Halloween news, Courteney Cox took her adorable daughter Coco door-to-door, and as cute as her little girl is, we can't help but focus on the Friends star's ample cleavage.

Is Miss Cox sexing it up to snag a new man?

Paris Hilton and beau River Viiperi weren't the only ones dressed as Batman and Robin!

Ashley Tisdale and her pal Kim dressed as the iconic duo last night, and the ladies looked like they were having a blast when we snapped them leaving a Halloween party in the valley.

The former High School Musical starlet tweeted, "Batman and Robin #nanana anananananananaBATMAN." Ahh, we love it when stars in sexy costumes post meaningful messages late at night! But when was the last time you saw Batman dressed like this?

We love how Katy Perry is bringing back the 90's with a costume inspired by MTV's Daria.

Perry, who rocked a black wig for her Jane Lane costume, struck a pose alongside her friend Shannon Woodward who dressed as Daria.

The 28-year-old "Firework" songstress looks vintage-ly delicious!

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Kate Moss and hubby Jamie Hince went to a Halloween bash in London on Wednesday night, and the couple dressed as Gomez and Morticia Addams! Gwen Stefani, Chloe Moretz and Mark Ronson were also at the party, which was hosted by British TV host Jonathan Ross.

This morning, Kate washed off every last trace of her spooky makeup and slipped into a leopard coat when we snapped her leaving her London flat:

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Lookin' good! And we still can't believe she spent years crying over ex-boyfriend Johnny Depp ... for more on that story, click here!

These two are too cute!

Jennifer Lopez and Casper Smart are currently on tour in Germany, but in the spirit of Halloween they decided to channel their inner flower child and don bell bottoms and flowers in their hair as '60's hippies!

The couple, who just celebrated their year anniversary, are definitely not shy about showing their love for each other on Twitter! "Happy 1 yr. anniversary to the most gorgeous, kind, sweet, funny, beautiful, lil bear in the world.... Love Bear #October25," Smart wrote to his lady love the other day.

When is the marriage proposal?!

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Paris Hilton and River Viiperi hit Greystone Manor's Halloween party ready to fight crime!

The gorgeous duo looked fierce ... with Princess P as a female Robin and her buff man sporting a Batman suit.

Talk about sexy crime fighters!

Leave it up to RiRi to change clothes in the middle of her own party!

Rihanna hosted a Halloween party at Greystone Manor in Hollywood last night, and the "Diamonds" singer walked the red carpet in a demure black dress before changing into a green veil and costume. Could she have been paying homage to her favorite past time?

Once inside, the Barbadian beauty partied with rumored on-again boyfriend Chris Brown, who was dressed as a Taliban soldier, and Basketball Wives star Evelyn Lozada.

Later in the night, Katy Perry's bestie was crowned the Queen of Halloween!

It must be nice to be the pop princess!

Riddle me this, riddle me that ... which family rocks Halloween costumes that are beyond phat? Oh, yeah ... the Kardashians!

Kim Kardashian put on her sexiest Catwoman costume while Kourtney showed off her post-baby bod in a skintight Batgirl get-up for a party at Liv Nightclub in Miami.

Kourt's sexy man Scott Disick rocked a Robin costume and Kim's BFF Jonathan Cheban killed it as the Riddler.

This group knows how to work it. Too bad Kris Jenner didn't show up as Wonder Woman.