Justin Theroux needed three layers of clothes to contain his private parts on the set of 'The Leftovers'.

The 43-year-old actor explained that he was forced to don multiple pairs of underwear after stylists on set of the police drama were worried about his manhood being visible on camera.

Talking about his ''flopping shlong'' with Conan O'Brien on 'Conan' on Wednesday night (03.09.14), Justin joked: ''There's two jogging scenes ... when I went to get my wardrobe for the second jogging scene way later, there was my jogging pants and two pairs of underwear in the trailer. I was like, 'Oh I can choose which pair?' They were like, 'No, they want you to wear both!' ''

Talk show host Conan then commented that the women in his office are obsessing over a scene where Justin - who is engaged to Jennifer Aniston - is actually wearing three pairs of underpants to protect his bulge.

The bashful actor replied: ''I don't know how to answer this question!''

To which Conan jokingly said: ''There's really not a question there, I'm just congratulating you!''

In the past, Justin's co-star Liv Tyler has commented on the star's prominent manhood, saying: ''There was quite a large bulge in his sweatpants, and it was all over. I get distracted when I watch the pilot, definitely. I'm like, 'Can't help but look there.' ''

Watch the full interview with Justin Theroux on Conan tonight at 11pm on truTV (freeview channel 68) - the home of larger than life characters in real situations.