CAMP PENDLETON — For football fans, it’s the Super Bowl. For followers of horse racing, the Kentucky Derby. Baseball? The World Series.

But for the weekend athlete who likes to run, jump, slither and dog-paddle through mud, it’s the World Famous Mud Run at Camp Pendleton, complete with hills, tire obstacles, river crossings, two 5-foot walls, a slushy tunnel, a slippery hill climb and, near the finish line of the 10K course, a 30-foot mud pit.

For the true mudder, it’s catnip — and on Saturday, 6,500 runners of various sizes and athletic accomplishments showed up to compete in the first of five races over three weekends. When it’s over, 32,500 contestants, 97% of them civilians, will have run, crawled and struggled for bragging rights.

“We’re the biggest and we’re the best,” said event coordinator Christina Chilleme, operations manager with Marine Corps Community Services, the mud run organizer.

Fun in the mud has long been associated with youthful rebellion, but the idea of mud running as a semi-organized sport has exploded in popularity only in recent years.

Organizations such as Tough Mudder, Muddy Buddy and Warrior Dash now host events throughout the U.S., some attempting to out-Ironman the Ironman contests and others geared toward the fun-loving.

A consensus in the mudder community suggests that the Camp Pendleton run, which dates to the early 1990s and has trademarked the name World Famous Mud Run, is the event from which others have sprung.

The contestants came from near and far Saturday morning, each paying $58. Last year, with three races, Marine Corps Community Services netted $1.5 million for programs for Marine families; this year, with five races — well, you do the math.

This year’s opening race featured more of everything: more contestants, more food booths, more bands, more outdoor showers, more portable toilets, more shuttle buses. And more Marines eager to explain to the civilians what they do for a living — like those stationed beside the M777 howitzers that can direct a shell at a target 18 miles away.

Many of the contestants were individualists, lean as whippets and determined to set a personal best. Others were members of teams, determined to break the finish line in unison and then head to the beer or food booths.

There were corporate teams, neighborhood teams, solo-gender teams, mixed-gender teams and teams made up of people from the same fitness club or school.

There was the “2 Legit 2 Quit” team, using a phrase from rapper MC Hammer or the movie “Hot Rod,” take your pick. “The Wild Ones,” three seventh-grade girls from Anaheim, were making their first appearance.

The “6:41" team, whose name is based on their habitual lateness to a 6:30 fitness class, was there.

There was also Laura Romero, 42, who wore a bridal dress and veil; her intended, Mark Imhoff, 41, wore a tuxedo T-shirt with a Styrofoam ball and chain on his leg. The Irvine couple are set to be married July 15.

The wives of Marines from a Special Operations battalion had a team, wearing pink tutus and tops that said: “Spartan Wife.”

Where were their husbands? “At home with the kids; it’s role reversal,” came the joyous response.

The “Slijivo Sisters” team was there. Slijivo is a Serbian plum brandy best downed quickly. The sisters all attend St. Steven’s Serbian Orthodox Cathedral in Alhambra.

No one has taken an in-depth sociological look, but organizers are convinced that mud runners are unique from your average dry-land runners attracted to the 5K and 10K races that seem ubiquitous on weekends.

“Mud runners are a different breed,” Chilleme said. “They’re a little wacky, and their idea of fun is getting down and dirty.”

Michael Erickson, 39, a medical supplies salesman from Sacramento, agreed. His team was dressed like rock stars from the 1980s.

“It’s dirty and it’s noncompetitive,” he said. “It’s perfect.”

tony.perry@latimes.com