Niall Horan is in the hot seat.
On Thursday, the "Nice To Meet Ya" singer joined James Corden for The Late Late Show's Carpool Karaoke—and it was filled with One Direction nostalgia.
Kicking things off, the duo sang "Slow Hands" together as they drove through Los Angeles. After making a quick stop in a park, Niall and James delivered a high-energy performance of his new song "Nice To Meet Ya," which launched the musical pair into some rock-n-roll dance moves.
As the song came to an end, James asked the "No Judgement" singer about his days in 1D and how he remembered that time in his life.
"Having looked at 1D from the outside now, I got to see, like, how big it was," he told the late night host. "'Cause when you were in the band, your work just becomes a bit normal and, like, you're in a little bubble and you don't get to see what it looks like from the outside. So, looking back now, I realize how lucky we were. Like, there was no one doing stadiums at the time. It's just insane."
Feeling nostalgic over Niall's One Direction days, James surprised him with his "favorite" piece of 1D merchandise, which happened to be a bottle of toothpaste with Niall, Harry Styles, Liam Payne, Zayn Malik and Louis Tomlinson on it.
"I actually brush my teeth with that every day," James joked. "I've got 17 fillings." Niall chimed in, "More sugar in that than a can of Coke."
Still on the topic of his boy band days, Niall recalled running into Kim Kardashian and her daughter North West backstage at an Ariana Grande concert, where he learned that Kim and Kanye West's little girl was a fan of the band.
"We were in the green room and Kim Kardashian pops in to see Ariana and she was with her little girl North," the "Little Town" singer began. "And then, how Kim described me to North was, ‘He's…this is Niall. He's the guy who sings from your toothbrush.'"
Before jumping into the next song, James whipped out another piece of 1D memorabilia: A Niall doll. After joking that he brought the doll from home, the Into the Woods star asked if 26-year-old Niall could share some advice to 16-year-old doll Niall.
"Your life's about to change ridiculous amounts," he said to the doll. "You're gonna go from living in a small town of about 30,000 people, to living in the biggest cities in the world. And, you're gonna play stadiums all over the planet in, arguably, one of the biggest boy bands of all time."
Staying on theme, James played One Direction's "Steal My Girl" and Niall channeled his inner boy-bander to sing the chorus.
Watch Niall relive his boy band days, face his fear of birds and take a lie detector test in the hilarious video above!