Duncan, who captained Wales to the side's 38-20 victory over the Pacific Islanders on Saturday said, "The bobble hats are a great way of raising money for Children in Need - and an essential fashion item when keeping warm and cheering us on at the Millennium Stadium.
"Adam and I are usually ok in the cold weather because we've got so much hair but many people are not so lucky so it's no surprise to me that the bobble hats have become so popular with Welsh rugby fans - and our fellow team-mates."
Fans of the Scrum 4 TV trails gang will know they're on a mission to raise money for BBC Children in Need on November 17th.
Inspired by Wales's Invesco Perpetual Series matches, the gang - Keith, Iestyn, Daf and a heavily pregnant Megan - are convinced they can raise money by selling red and white striped Wales-Cymru bobble hats outside the Millennium Stadium before the games.
The previously unfashionable acrylic hats have since become the fastest-selling fashion accessory in Wales, helped by celebrities including Big Brother star Imogen Thomas and former Wales captain Gareth Davies who have modelled them. The hats are even set to star in Welsh language soap Pobol Y Cwm.
With Children in Need night this year coinciding with Wales's clash with Canada, Scrum 4 will be pulling out all the stops to get their stock shifted before the big match. But in the real world the hats have been flying off the shelves at WRU outlets and phonelines have been inundated with people trying to get their order in.
"We're selling more than a thousand a day," said the man behind the Scrum 4 trails, BBC Wales Head of Promotions & Branding, Phillip Moss. "The support from the WRU has been tremendous and with Wales players leading the way by buying the bobble hats too, we're now preparing for a rush as people try to get their hands on the hats."
Fans can snap up one of the limited edition bobble hats by phone - call free on 08000 566 424 - online at bbc.co.uk/pudseywales and on match days from WRU outlets at the Millennium Stadium, Cardiff.
The hats cost £6 including P+P - or £5 at the Millennium Stadium, with at least £2 going to Children in Need.
However, the fun doesn't stop there and the WRU's title sponsors for the November series of matches, Invesco Perpetual, are also putting their hands in their pockets. They will donate 'a significant figure' to the Children in Need fund if the original man mountain, Scott Quinnell, manages a feat he has never before achieved - he will attempt a penalty goal at half-time at the match on Friday night - a sight not to be missed!
All this will add to the family atmosphere at the Millennium stadium on Friday night. The pre-match entertainment will star 10-year-old Cardiff harpist Benjamin J Creighton Griffiths who has already raised over £6 500 for Children in Need by selling his own harp recordings. Co^r Cymru 2005 winners Serendipity will also perform before the game.
And with over 60 000 tickets already snapped up at £10 (adults) and £5 (children) for Friday night's clash with the Canucks, fans are being urged to get their tickets early to avoid disappointment on the night.
Tickets are available from Ticketmaster on 08705 582582 / www.ticketmaster.co.uk - or to personal callers at the Millennium Stadium ticket shop, 98 St Mary Street.