'You don't send a guy pictures like this': Justin Bieber shows his underwear in sagging trousers...as Mark Wahlberg complains about the pop star sending him modelling shots

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Justin Bieber is apparently quite fond of showing people his underwear, regardless of whether or not they want to see it.

The 22-year-old was spotted on Thursday strolling about in Toluca Lake, his trousers sagging to the point they revealed quite a lot of what was beneath them.

On Wednesday, Mark Wahlberg had said on Conan that, to his bemusement, the pop star had sent him some Calvin Klein modelling shots in which Bieber wore nothing but boxer briefs.

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When you got it, flaunt it: Justin Bieber was spotted on Thursday strolling about in Toluca Lake, his trousers sagging to the point they revealed a fair bit of his underwear

As he headed down the pavement on Thursday, the Sorry singer's tight undergarment gave a well-defined impression of his toned rear end.

A white T-shirt showed off the sprawl of tattoos up both his arms, and he'd popped on a pair of matching white trainers.

On Conan, the Boogie Nights star - who'd himself underwear modelled for Calvin Klein, back when he was known as Marky Mark - called Bieber his 'friend.'

A clear view: As he headed down the pavement, the Sorry singer's tight undergarment gave a well-defined impression of his toned rear end

The Love Yourself singer, who's been the face of the brand since 2015, is 'a very nice young man,' per the The Departed actor, who's 'spent time with him.'

As Wahlberg told Conan O'Brien: 'He did send me the picture. I was like: "You don't send a guy pictures like this of you in your underwear."'

The chat show had shown one of Bieber's modelling shots right next to one of Wahlberg's. In his photo, the erstwhile rapper grabbed his own crotch and pursed his lips haughtily at the camera.

Excessive exhibition: On Wednesday, Mark Wahlberg had said on Conan that, to his bemusement, the pop star had sent him some Calvin Klein modelling shots in which Bieber wore nothing but boxer briefs

Taking an understanding tone, the film star noted that when Bieber had sent the photo, 'he was proud! You know, it was a big deal for him to do.'

Yet and still, 'I was like: "You know, I am at 45, and a dad, and a husband and father of four, and basically trying to move away from that image."'

He went on to note that 'people give him flack for, you know, being, you know, kinda growing up in the spotlight, and he's, you know, they say, has a bit of an attitude. But you look at the look on my face; I mean, I was the biggest punk in the world.'

Passing the torch: On Conan, the Boogie Nights star - who'd himself underwear modelled for Calvin Klein, back when he was known as Marky Mark - called Bieber his 'friend'

His Calvin Klein photo, in which his only article of clothing besides his underwear is a CK beanie, reappeared on the screen alongside Bieber's.

As the Boston native pointed out, the Canadian singer's expression in his picture seems 'very nice, young and polite, compared to what I was.'

O'Brien quipped: 'You look like you're just causing yourself pain by squeezing your s-...', getting a laugh from his guest and adding: 'That is the face you make when you squeeze your sac like that.'

The former Marky Mark And The Funky Bunch frontman went on to refer to his old Calvin Klein gig as 'not one of my proudest moments.'

Wrong audience: As Wahlberg told Conan O'Brien: 'He did send me the picture,' to which 'I was like: "You don't send a guy pictures like this of you in your underwear"'