ATLANTA—This Labor Day weekend 85,000 people are expected to attend “Dragon Con,” an annual convention of comic book, superhero and fantasy fans—one of the largest such gatherings in the country.

Some of them will celebrate a hotel carpet that was ripped out years ago.

Members of the Cult of Marriott Carpet will walk the convention halls and march in a parade wearing costumes in the hypnotic, star-circle pattern of blue, red and gold that once covered the atrium floor in one of Dragon Con’s chief venues.

Zan Bowden, a 45-year-old IT worker from Florida, organized the first group to wear the pattern in a Dragon Con parade in 2016. Ms. Bowden, who posted notices on social media, wasn’t sure anyone would show up. People came in all kinds of costumes, including what she described as “a carpet warrior with a shield” and “a Picasso-inspired outfit.” Some made their costumes from actual carpet.

“I got 30 random strangers to dress up like carpet and march with me,” she said. “You should have heard the cheers of the crowd.”