The Secret to James Corden's 'Carpool Karaoke' Success (Video)

And the result is pure gold, each and every single time.

The sketch has become a viral phenomenon, turning Corden into a global personality in the process, and even spawning its own spinoff series coming to Apple Music later this summer.

"Outside of like YouTube, when we launched two years ago, we were on in like eight countries. And I think we're now on in 152 and that growth is really only down to the show's relevance on the internet which makes other territories say, 'We want to buy that show,'" Corden explains during a new appearance on "The Bill Simmons Podcast."

As for the aforementioned rules to making Carpool Karaoke magic happen, Corden revealed many of the behind-the-scenes details that go into making each segment.

On drawing a hard line when it comes to the stars they'll let participate…

"As soon as that segment felt like it was a thing and was becoming a thing, we felt like we had to implement our own rules really and go, 'OK, we have to sort of try and protect this.' … We have to preserve this only for the biggest or most relevant music artists in the world – and that's it. We cannot break that rule… Nothing would give me more joy than getting in the car and driving around singing songs with Will Ferrell… it would be amazing TV. But, we feel like we have to keep it in that sort of rarefied air because that's the only way it will sustain itself, really."

On how it happens far less often than you might think…

"Look, we could do it every week if we wanted. We've only put out two this year and they were in the last eight days… We never put a number on it because it just comes around to who's got albums out, who do we think is interesting, who's got a tour to promote."

On who is on his ultimate celebrity wish list…

"Of course, there is a list of names where you're like, they're the golden names. If Billy Joel is around – nothing would give me more joy than doing it with Billy Joel… He's amazing."

On where they shoot them and the actual logistics of pulling it off…

"It depends where we are. The Adele one we did in London. The Madonna one we did in New York, but predominantly we're here [in Los Angeles.] We drive in a convoy. There's a car in front of us, two cars behind us and one car that will drive around or alongside and get exterior shots of the car. The rule is we just drive in a straight line away from the sun… so you don't get like weird mirror shadows on your face… It's Los Angeles, so you're driving in increments. I'm driving in Hollywood between the hours of 10 a.m. and 5 p.m. where really, how fast can you ever be going?"

The first "Carpool Karaoke" segment debuted March 25, 2015 in the third episode of "The Late Late Show," featuring Mariah Carey as Corden's first "Carpool" passenger. Since then, there have been a total of 33 "Carpool" sketches to grace Corden's show, with a couple specials and more sing-a-longs in the not-so-distant future.

Here are 5 unforgettable "Carpool Karaoke" segments:

Who can forget Corden and Adele belting out "Hello" and "Someone Like You" while driving around London! The highlight, though, comes as Adele surprises the host – and all of us! – by rapping along to Nicki Minaj's "Monster."

We love pretty much anything Gwen Stefani does, and Corden having her act out different emojis was amazing. But the highlight here comes when they stop to pick up two surprise guests – George Clooney and Julia Roberts – who join in for a performance of Gwen's "Hollaback Girl." Truly B-A-N-A-N-A-S.

It's Carpool Britney, bitch. Brit rolls around Hollywood, singing her hits, talking about her life – and then somehow doesn't lose it when Corden dons her signature sweater, blouse and pigtails from "… Baby One More Time."

The sketch that started it all. Done as part of Comic Relief in 2011, Corden (in character as Smithy from his British sitcom "Gavin & Stacey) cruises around with the "Faith" singer by his side. The duo belts out some of George Michael's all-time greatest hits, including "Freedom" and "I'm Your Man."

Billy Joel may be at the top of Corden's wish list, but Elton John ain't exactly chopped liver! The sketch aired as part of the post-Super Bowl 50 show on CBS. Cue the sunglasses, the feather boas, and some of Sir Elton's greatest hits!