Lewis Hamilton couldn't stop grinning. Neither could Tony Stewart.
After trading cars at Watkins Glen International on a damp, cold Tuesday afternoon – Hamilton drove the No. 14 Chevy from NASCAR's Sprint Cup Series and Stewart drove Hamilton's championship-winning McLaren Mercedes from 2008 – both drivers were elated.
Hamilton had his mobile phone out for most of the day, snapping pictures of Stewart, the cars, the drivers together, the track, the fans and even the media.
"I just feel like a kid today," said Hamilton, the über-celeb who dates the lead singer of The Pussycat Dolls. "It's good to be a kid again."
Stewart, meanwhile, said sitting in a Formula One car was "truly the experience of a lifetime" and said he enjoyed the ride so much that if he knew what it felt like to drive an F1 car 20 years ago instead of discovering it on Tuesday, he might have never done NASCAR.
Hamilton's impression of a stock car?
"I was a little bit nervous," Hamilton said. "I was really, really surprised – I didn't know how stiff it was going to be, but it handles really well."
"Once we got rolling, it was unbelievable," Stewart said. "...Amazing of what the capabilities of the cars are. It's probably going to make my crew chief a little more stressed during the weekends right now because I'm going to want it to handle like that all the time. I don't think we'll ever get it there."
The day started under drizzly skies, and Stewart clutched a cup of coffee as the vapors drifted skyward in the cold air. He looked up into the precipitation and winced as if to say, "Not today!"
But there was nothing he could do about Mother Nature. Though the rain eventually quit, the track was still damp throughout the hot laps (Hamilton called it "British weather").
Hamilton and Stewart, clad in their driver uniforms, jumped into a black SUV to take a reconnaissance lap together. Stewart drove the first couple circuits and showed Hamilton the layout and braking points; then they switched spots.
As the fans realized who was in the SUV zooming by – Stewart honked several times on the frontstretch – they exploded in cheers.
The drivers then retreated to their makeshift garages, where each showed the other about the nuances of the vehicles.
Hamilton pulled out his phone to take a picture of a Sprint Cup Series engine and poked his head inside the car. The drivers spent a great deal of time looking at the F1 car, as Hamilton crouched down and gestured to various parts of the vehicle, explaining the various details while Stewart shook his head in apparent amazement.
The drivers then met the media – international reporters probably out-numbered the NASCAR beat writers at least 2-to-1.
Did Hamilton know much about NASCAR? Yes, he said, but didn't think other F1 drivers necessarily did.
"We're not massively exposed to it," he said. "It's a bit like Formula One (is) over here. But those of us who take a keen interest in it read up about it in magazines and online – and we have Speed channel."
What did Hamilton think of NASCAR drivers?
"I won't know until today just how difficult it is," he said. "...But over in Europe, we have a huge amount of respect for NASCAR drivers."
Before trading rides, Hamilton and Stewart took a few laps in their own cars to make sure it was set up properly for the other driver. Hamilton was up first, giving a thumbs up to the cheering crowd – there were roughly 5,000 people who braved the weather – and waving both hands to answer the air horns and shrieks of "Lewis!" before he climbed into his car.
As the McLaren Mercedes screamed down the frontstretch – the first modern F1 car to take laps at Watkins Glen since the circuit departed in 1980 – it was greeted by flashbulbs, cheers and the waving of a few British flags. Some fans had driven as far as 21 hours to see the seat swap spectacle.
Once Stewart took a few spins in his Chevy – which he described as "a little sketchy" with a windshield wiper and rain tires – it was time for the swap.
Hamilton, under Stewart's watchful eye, began to climb into the stock car and paused once he got both legs inside the cockpit.
Looking around at the photographers and guests of event sponsor Mobil 1, Hamilton offered a wide grin.
"This is going to be fun!" he said.
He had someone take his picture once he was strapped into the car – flashing the peace sign in the process – fired up the engine and rolled off pit road.
The car disappeared out of view, but the sounds of the engine could be heard in the distance as Hamilton got up to speed around the "long course" at Watkins Glen.
Suddenly, Hamilton came roaring around the final turn and onto the frontstretch, zooming past the grandstand at what seemed like full speed.
To the untrained eye, it would have been impossible to tell whether it was Hamilton or Stewart in the car. The 2008 F1 champ posted lap times that were comparable to Stewart's and improved by one second on each of his first three laps.
On the final lap, though, he nearly lost it. Hamilton drifted from the final corner onto the main straightaway, and the fans oohed and aahed as he saved it.
Sensing his run was over – but not wanting the fun to end – Hamilton drove to the start/finish line, where he did an impromptu burnout to the delight of the crowd. The fans erupted as Hamilton smoked the tires and disappeared into a huge cloud.
Not bad for a guy whose lone stock-car experience had been playing with miniature diecast cars as a kid.
Then it was Stewart's turn. As roughly two dozen photographers from all over the world captured the moment, Stewart fulfilled a major item on his bucket list by sliding into the seat of the McLaren Mercedes.
Stewart did well on his laps, but was certain he didn't come close to the car's capabilities. He estimated he drove it to about 80 percent of what it could do, then guessed the car had probably another 20 percent he didn't even know existed.
"What stood out the most is how incredibly good and efficient the brakes are," he said. "It's just amazing how far you can charge the corner."
Hamilton said there were little similarities between the cars aside from the basic skills it took to drive them.
"(The cars) are completely different, but the driving skills that you learn – the controlled braking into corners, the part-throttle, on-throttle, shifting – made it easier to pick it up quicker than perhaps others would," Hamilton said. "That's why Tony went out there and straightaway picked it up, no problem."
Hamilton said he could see himself "having more fun with that," and joked that with his recent performance in F1, he should consider switching to NASCAR.
But in all seriousness, Hamilton said he has much more to accomplish in Formula One before he ever thinks about leaving for another form of racing. He'll likely re-up with McLaren, he said, since the team remains competitive.
If Hamilton ever did leave F1 and bring his star power to NASCAR, Stewart had just one request.
"I just want first dibs on trying to hire him," the owner/driver said.