Kendall Jenner Calvin Klein Underwear Ads, Justin Bieber Underwear Ads

You may think you’ve seen
Kendall Jenner
and
Justin Bieber
‘s ads in every possible permutation, but we guarantee you haven’t seen them quite like this yet. The two stars (along with music heavyweights like
Kendrick Lamar
, Fetty Wap and
FKA twigs
) strip down, glam up and give good smolder in the brand’s latest ads, and we’ve got an exclusive peek behind the scenes.

Tyrone Lebon

Bieber in particular had a blast on set after his sultry (but serious) black-and-white shoot from last January. “It was much more informal this time around. I was excited I got to skateboard,” he tells PeopleStyle. And lest you think it’s at all awkward to get down to a very tight pair of boxer-briefs in front of a crowd, let Bieber reassure you: “I’ve been doing photoshoots since I was a kid, so I am comfortable in those situations at this point.”

Jenner, on the other hand, says she’s a bit more shy — that is, until the camera starts clicking. “Explaining that kind of thing with words is always tricky, but it’s just this rush and a big part of what attracted me to modeling in the first place,” she tells PeopleStyle. Equally exciting? Seeing her face (and abs, and everything else) huge on billboards.

Tyrone Lebon

“It’s a bit unreal to see myself in such an iconic ad … that I’ve grown up obsessing over each time I saw it’s campaigns in magazines,” she says. “You know that feeling you get when you’re hitting the loop to loop on the roller coaster and your belly drops and you get that rush of adrenaline? That’s kind of what it feels like. Now combine that with a giant billboard on [N.Y.C.’s] Houston St. and you’re just like, Wow.”

One thing Bieber and Jenner definitely have in common with their model instincts? They love great music to get them in the right mindset. “All you really need is a good playlist and the rest sort of falls into place,” Jenner says, while Bieber (who had his new album Purpose playing during the shoot) echoes, “It depends on my mood. Sometimes, I want it to be calm and other times I want to be really hyped — so it all depends.”

Tyrone Lebon

Luckily, they had plenty of great music right at their fingertips, thanks to artists including Kendrick Lamar (pictured), FKA twigs (you might also know her as Robert Pattinson’s fiancée) and Fetty Wap filling in the blank to the statement “I ______ in my Calvins” for a series of dramatic, colorful ads shot in L.A. by Tyrone Lebon. And for the first time, all of the CK lines (denim, Collection, underwear … you get the idea) are all presented in one ad campaign, mixing the brand’s different aesthetics in the same way that their models mix genres.

RELATED VIDEO: First Look: The 90-Second Spot for the Ad Campaign!

Tyrone Lebon

A typical day for Bieber is as follows, he tells PeopleStyle:
8:00 a.m.: I sleep in #mycalvins
3:00 p.m.: I skate in #mycalvins
12:00 a.m.: I record in #mycalvins

He also gets plenty of free underwear out of this gig, in case you were worried: “They know me pretty well, so the Calvin team know what I like and what fits well. They send me underwear every month so I usually don’t take much home with me from shoots.”

Tyrone Lebon

And for Jenner, who loved working with the other models on the campaign, she answered the questions thusly:
I sleep in #mycalvins at 8am
I laugh in #mycalvins at 3pm
I am laughing so hard I’m actually crying real tears in #mycalvins at midnight

Most importantly, though, she’s got some great advice for anyone wearing underwear, even if you won’t be seen in yours on the side of a building 40 feet high: “The move is to just feel good in them. When you feel confident, you just radiate and operate on a totally better vibe.”

For more from the ad campaign (including a truly great quote from Justin Bieber) pick up this week’s issue of PeopleStyle on stands!

— Alex Apatoff