Don't miss the happening doggie Halloween party tomorrow at the Hawaiian Humane Society.

The Muttster Mash, a benefit for the Humane Society, is sponsored by pet-friendly businesses that care about animals: The Hawaii Pet Nanny, Island Dog Magazine and the Pet Hui. The last event was in 2007. This year about 100 dogs in their costumes are expected to be at Hawaiian Humane Society's McInerny Park from 10 a.m. to 1 p.m.

John Harmon, co-founder of Island Dog Magazine, says, "The purpose of this event is to highlight the park and have fun with your dog."

"We will have adoptables at the party as well," says The Hawaii Pet Nanny's Tammy Kubo. "We hope to bring awareness to the Hawaiian Humane Society, their dog park and the work they do."

Everyone is joining in on the fun. A Girl Scout troop will be on hand to help with the festivities.

The grand prize for the costume contest is a one-night stay at Hotel Renew, a pet-friendly hotel, along with a pair of Hotel Renew slippers.

Besides the costume contest, there will be a parent and doggie parade led by adoptable "grand marshals."

The admission is free, but the co-founders hope that pet food and toys like "kongs" will be donated.

To accommodate the crowd, extra parking will be available at Prince Kuhio Elementary School across the street.

Treats will be given to the first 200 participants.

Don't forget your camera!