Don’t eat the brown GU: things get weird at the scream scram in dowtown denver. Courtesy of Free Lunch Photography.com/ Boys & Girls Clubs 2011 Scream Scram

Make your Halloween costume serve double duty—wear it in an endurance race, then wear it to trick, treat and party (or, um, recover). To help, here’s a list of our favorite costumed extravaganzas in Colorado.

DENVER MONSTER DASH 5K: October 13 • Denver

The folks who put on the popular Monster Dash in Old Town Louisville (see Oct 27 below) are introducing the race to Denver. Taking place in the Lowry neighborhood, the dash promises the same family-friendly atmosphere with an après-race costume competition, the Monster Mini Mile (a 1-miler for kids of all ages) and a Spooky Sprint 100-meter kids’ race. Your $25 entry fee includes a creepy tech t-shirt. monsterdashrun.com

SCREAM SCRAM RUN: October 19 • Denver

A fundraiser for the Denver Metro Girls and Boys Club, this year’s race will be particularly bewitched—it’s the 13th annual. Held on a Friday night at Wash Park, the Scream Scram begins with a costume contest wherein participants walk the orange carpet to show off their garb, and ends with the Trick-or-Treat Street Festival. bgcmd.org

ZOMBIE CRAWL: October 20 • DENVER

Not so much a race as a parade down 16th Street (followed by a rocking after party at City Hall), the Zombie Crawl is nonetheless not to be missed. When else can you say you attended the largest zombie gathering in Colorado history? If you’re looking for more active endeavors, register on Active.com for the “Organ Trail” adventure race happening beforehand at 11:00 a.m. eyeheartbrains.com

DENVER GORILLA RUN: October 27 • Denver

Now in its ninth year, this ridiculous 3.5-mile race puts participants in full gorilla suits to benefit the Mountain Gorilla Conservation Fund. Choose to run, walk or bike the course, which starts and ends at the Wynkoop Brewery. The suit is yours to keep, and included in the $99.95 entry fee. There are even suits for kids, for a $50 entry fee. Got a suit from last year? Register at a discounted rate. denvergorillarun.com 

PHANTOM 4-MILER: October 27 • Loveland 

This 4-mile race, now in its third year, benefits the Larimer Humane Society, Animal House and Denkai Animal Sanctuary. Dogs are, of course, encouraged to participate. Last year’s event drew 300 human runners and raised $8,000. The race starts with a costume contest (for people and dogs) and includes a Bone Chilling Breakfast at the Embassy Suites Loveland. phantom4miler.com

THE LAST RUN OF YOUR LIFE: October 27 • Fruita 

This rowdy 5K requires dodging freaks and ghouls as you run the Big Salt Wash Trail. Participants wear a belt of flags, and those who make it to the finish with at least one flag left are eligible for special prizes. Everyone is eligible for the free beer. A portion of your $40 entry fee goes to the Grant a Wish Program, helping local youth learn life skills through Parks and Rec departments across the Grand Valley. kekbfm.com

MONSTER DASH 5K: October 27 • Boulder

This costumed race through Old Town Louisville doesn’t start until 3:00 p.m., which means you could make it a doubleheader by doing the Denver Gorilla Run first at 11:00 a.m. Not sure how all that fur would smell afterward, but perhaps the primal scent will earn you authenticity points in the costume contest following the race. monsterdashrun.com

THE MELTING POT HALLOWEEN HUSTLE: October 28 • Littleton

The 5K-course through downtown Littleton on the Platte River path begins and ends at The Melting Pot, which means chocolate fondue for all. Geared toward families, the event includes a costume contest for adults and children, trick-or-treating, face painting, bounce houses and haunted tours of the Melting Pot. hallucinationsports.com