Matthew Mcconaughey is stunned people keep telling him they've seen him ''buck naked'' in his new movie.

The 49-year-old actor - who has children Levi, 10, Vida, nine, and Livingston, six, with wife Camila Alves - insists he has no recollection of stripping off more than his shirt in 'Serenity' so he's keen to take a closer look at the finished film.

Asked about being ''buck naked'' by 'The Late Show' host Stephen Colbert, he said: ''That's what I keep hearing. I'm going to the premiere tonight, and I've got to see if there's a new edit or new cut of this film that I haven't seen.

''I know that I was topless, and I've got people coming up and going, 'Oh my God, it's great to see you full frontal.' And I'm like, 'What?' Was it really? Was I?' ''

The host quipped: ''Will that be the first time you find out whether you're cut?''

In response, Matthew made a saucy pun about Wild Turkey Longbranch, his own brand of bourbon that he'd brought on set for Stephen to try, and the presenter's own liquor, Savage Cock.

He laughed: ''Speaking of bourbons that you and I love, it'll be the first time we found out if I have savage cock or longbranch.''

Because of his guest's disbelief about being naked in the movie, Stephen produced a still which seemingly showed the actor jumping off a cliff while nude.

But Matthew insisted: ''I'm pretty sure I've got a nude coloured thing that's holding bits from being dangling, you don't want to jump from something that high with bits not where they're supposed to be.

''That cliff's about 60 feet. I did do that jump once.

''It is kinda painful, there's a few things you have to learn - if you do have dangly bits, keep them very secure because I'm telling you I'm not just flapping in the wind, I would be injured right now if I was.''