Since then, Normal Bob has become a daily fixture in the park. He is relatively unremarkable by downtown Manhattan standards — cuffed jeans, Doc Martens shoes, anarchist shoulder bag — but he presides over the cast of characters who play upon the giant stage that is the terraced south section of the park facing 14th Street.

“I started realizing there were all these different groups here, and it was all the same people every year,” said Normal Bob, 41, whose given name is Bob Hain. His professional name is Normal Bob Smith; he is a graphic artist who lives in Bushwick, Brooklyn, and runs a provocative Web site,

In Union Square, Mr. Hain is not interested in the Greenmarket or the art vendors, or the grandmaster chess players taking on all comers for $10 a game. This is all too normal. He is interested in the regulars who consider the park their living room, and its denizens their family. For this set, Mr. Hain is equal parts referee and ringmaster, curator and chronicler.

There is Junky the Barbarian, Pretty Boy Jake and Green Graver Girl, for starters. Then there are the categories of park regulars, which include scenesters, peepers, fundies, gravers and Griswalds.

Mr. Hain calls all these people his Amazing Strangers, and celebrates hundreds of them on a section of his Web site with the same name. Last year, he created a hall of fame, selecting the most outlandish characters and creating cartoon versions of them. Of the 70 cartoon characters he created, he selected about half to form an all-star lineup, then put them on a postcard-size handout challenging people to match each character with the right nickname.

The handout’s reverse side is an aerial photograph of the park with diagrams indicating where the various cliques and subsets tend to gather. For example, it shows that the peepers gather at the south side of the park, so they can blend in with pedestrians while peering under the skirts of women sitting on the steps. The gravers — Goth-ravers who usually dress in wide, black Tripp pants — gather nearby, near the statue of George Washington. The drug addicts do their nodding in the rear of the park, on the benches toward the east side. The Griswalds, or naïve tourists, gawk at it all from the periphery.

The club kids known as scenesters remain aloof, gathering on the triangular minipark toward Park Avenue. Fundies — being the fundamentalist Christian preachers — tend to gather at the very southwest corner of the park.

The blog portion of Normal Bob’s site unfurls like a daily soap opera, updated frequently with photographs and video footage of arguments or fistfights between park regulars, or updates on new outfits or routines. There is often a video analysis of the techniques of the park’s most prominent peepers, who tend to be slovenly looking middle-aged men with highly developed ways of stealing glances.

With photographic examples and flow charts, Mr. Hain lays out the various categories of the various sets of downtown young people who hang out in the park.

There is a primer on distinctions between a Goth and a raver. Then there is the graver, whose name borrows from both of those, but who would not be caught dead being grouped with either.

By contrast, the hipster is a bird of another feather, “the natural enemy of the graver,” Mr. Hain says. And the scenesters are the result of melding hipsters and gravers, identifiable by their studded belts, tight clothing and maybe a black handkerchief in the back pocket.

Then there are the robo-trippers, who try to get high by “huffing,” or inhaling, products like Dust-Off, or by drinking Robitussin.

One recent Saturday, Mr. Hain sat near the George Washington statue, along with his usual sidekick, “Skater” Bob Crawford, 38, from Kearny, N.J. It was a typical day for the two Bobs: cheap eats at Taco Bell and trips to the bathroom at Whole Foods.

Things are slower these days, with part of the park annexed by the artisan kiosks of the Union Square Holiday Market. Behind the statue, a few obviously inebriated men milled about and at one point, a sloppy fight broke out.

“I don’t have names for those guys,” Mr. Hain said. “They’re not on the handout. One time, one of them asked me, ‘Why don’t you have us listed?’ I said, ‘What are you?’ He said, ‘We’re dirtbags, put us on there!’ ”

Mr. Hain grew up in a devout Christian family and is now a devout atheist, and has identical tattoos on each arm of Satan being crucified. He has gotten his share of media attention for creating a product called DressUp Jesus, an irreverent refrigerator ornament that allows the user to bedeck Jesus on the cross in silly outfits. The product became widely controversial a few years back after a chain store began stocking it. He still sells some to gift stores in Manhattan, and he still gets plenty of angry e-mails from offended Christians, which he prints on his site with his responses.

He is proud of the fact that if one does a Google search on the word “Jesus,” his Web site comes up as the second-highest ranked, after Wikipedia’s Jesus page.

Recently, a crusty man with hobo whiskers and a few crooked teeth in his mouth walked around the park soliciting change by flashing first one cardboard sign — “What’s the best nation?” — then the other — “Donation.”

“His name is Signs,” Mr. Hain said.

“We’re all family here,” said Skater Bob, and Normal Bob laughed and went back to monitoring his Amazing Strangers.