Since Beijing, Phelps has enjoyed his longest break from training ever. He's on a victory lap of sorts, touring the country and building the Michael Phelps brand. He let us tag along with him, and gave CNN's Anderson Cooper his most extensive interview since the Olympics.
He explains how he won in Beijing, how he almost didn't, and what life is now like for an unassuming 23-year-old swimmer who's also the greatest Olympic athlete ever.
At the red carpet at MTV's Video Music Awards in Hollywood, the loudest screams were not for a rapper or a rocker or the usual suspects: they were for Michael Phelps, a guy who can barely carry a tune.
The next day, he had an appearance on The Tonight Show with Jay Leno, then a red eye flight to New York, where he helped open the stock exchange the next morning.
But Phelps was starting to show the wear and tear of a tour that had taken him from Beijing to Portugal, and to San Francisco among other stops.
By mid-September, he had not been home for three months. 60 Minutes caught up with him in New York, between a commercial shoot and a rehearsal for Saturday Night Live.
Asked if he worries he's doing too much, Phelps told Cooper, "No, cause I'm having fun. You know, it's like (yawns), excuse me, you know, after I…"
He has no trouble sleeping, telling Cooper he can fall asleep within seconds. "Probably within a minute I could, I could be out cold."
Sure enough, Phelps started nodding off. "It took you 50 seconds to fall asleep after we stopped. We actually timed it," Cooper pointed out.
"I was exhausted that day," Phelps replied, laughing. "I was really tired that day."
"Are there moments when you're like, 'This is just nuts?'" Cooper asked.
"There have been a few times where I'll be like, 'Wow this is, you know, more than I expected or more than I thought would happen,'" Phelps admitted.
What's happening is a just reward for a guy who's been training non-stop since age 11. His teenage years were spent swimming lap after lap, thousands of hours staring at a black line on the bottom of a pool.
"For about five years he did not take one day off," explained Phelps' coach Bob Bowman.
Bowman said Phelps even trained on Christmas Day and on his birthdays.
"How do you do that every day?" Cooper asked.
"To be honest, it's not wanting to lose, wanting to do something no one's ever done before. That's what got me out of bed every day," Phelps explained.
The workouts were so intense, Bowman became known as the mad scientist. The toughest workouts, he said, were swimming 10,000 meters for time, which takes about two and a half hours.
"Two and a half hours of full-out racing?" Cooper asked.
"Just swim as hard as you can for two and a half hours," Bowman explained.
"Like horrible, horrible workouts. When you see them on paper, you're like, 'I can't do this.' He makes us do it so we're more confident and we know that we can do anything that we put our mind to," Phelps said.
Payoff came at the 2004 Athens Olympics. Phelps won six gold medals, an extraordinary achievement but he just missed Mark Spitz's record of seven golds.
Then came Beijing and a chance to make history. To win eight golds, Phelps needed to swim 17 times in nine days. So many things could go wrong in Beijing - and they did. In the 200-meter butterfly final, his goggles filled with water virtually from the start.
"They started filling up more and more and more. And about 75 meters left in the race, I could see nothing. I couldn't see the black line. I couldn't see the T. I couldn't see anything. I was purely going by stroke count. And I couldn't take my goggles off because they were underneath two swim caps," he remembered.
Somehow, he not only won his fourth gold medal of the games, he also set a world record.