Pereira established the mark on Saturday with gold in the 200-meter breaststroke, breaking the 40-year record held by Mark Spitz. He added a silver in the 400 medley relay and a bronze in the 100 backstroke on Sunday.
"I'm just an athlete who trained really hard to get where I am. I'm a normal swimmer," the 21-year-old Pereira said.
Normal? Not for some.
"Gold Fish," read a headline in the Rio sports daily Ataque.
"Stroking into History," said Rio's O Globo.
He's no overnight sensation, though.
At the 2003 Pan Ams in Santo Domingo, Pereira won a silver and a bronze. He's had some big victories since, but was no big star heading into this meet.
Born in the industrial city of Volta Redonda, Pereira hung out at the pool during a boom in Brazilian swimming. It was the prime of Gustavo Borges, who won the silver medal in the 200 freestyle at the 1996 Olympics, and Fernando Scherer, who took four golds at the 1999 Pan Am Games in Winnipeg.
Pereira was 10 years old when he was watching TV and saw Scherer win a bronze medal at the '96 Olympics in Atlanta.
"I grew up following Gustavo and Fernando in the pools," said Pereira, still not accustomed to his status as their successor. "I still haven't felt all the repercussion. We're still in the rhythm of pool-villa, pool-villa," referring to his routine of training and returning to the athletes village.
Pereira surpassed former swimmer Djan Madruga as the Brazilian with the most overall medals at a single Pan Ams. Madruga won three silvers and three bronzes in San Juan in 1979.
Concentration is his great asset, Pereira says. But the stir he causes when he walks by is noticeable, especially among the teenage girls who call to the curly haired swimmer with a silver earring on his left ear.
The fuss is good, he says, if it brings more financing for swimmers.
"I hope there's an increase in support, especially in the developing categories of younger swimmers, where it's needed the most," he said. "Some kids just stop when they're halfway there, at 15."
Are six gold medals, a silver, a bronze and a handful of Pan Ams records his limit?
His countrymen have elevated him to star status thanks to his performances in Rio. And they have taken Pereira to heart. Fans cheered wildly in the Maria Lenk Aquatic Complex as he put on a burst of speed in the final 50 meters to edge Brazil's Henrique Barbosa by 0.32 seconds to win the record-setting sixth gold on Saturday.
"How about that Thiago Pereira? He's phenomenal! He's the Lewis Hamilton of swimming," said taxi driver Giovanni Couto, referring to the British driver leading Formula One.