The Barbarians' dressing room wasn't just full of hype after the side claimed an unlikely 38-35 win over the Pumas on Sunday morning (NZT).

A video posted by the club, which has since gone viral on social media, has revealed the extraordinary way the iconic team prepared before taking to the field against Argentina at Twickenham.

Rather than forming a team huddle or reinforcing game plans, the Barbarians broke out into passionate song just minutes before kick-off, singing 'He'll be coming round the mountain Malcolm Marx' led by South African lock Lood de Jager.

The team grew increasingly louder each time the verse repeated with many of the player's fist pumping and jumping up around each other.

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The video has since been shared on Twitter with many fans applauding the team's amusing approach.

Down 28-7 in the first half and 28-14 at halftime, things didn't look good for the Baabaas as the Pumas dominated.

But with bellies still full of this week's bonding, and perhaps some more hype from a halftime installment of their pre-match song, they rallied to create a late try for de Jager before replacement playmaker Elton Jantjies stepped up.

It was a fairy-tale finish for All Black and Barbarians captain Wyatt Crockett, who bowed out of the highest arena after battling for 44 minutes on the field.

After toasting this victory in typical Baabaas style, Crockett will immediately resume store duties.

"I always hoped to play for the Baabaas," Crockett said. "I've watched from afar a lot of my good friends have played for this team and they've all said it is one of the best weeks of their rugby careers and it's so true.

"It's pretty cool to play here in this stadium, in this arena, for my last international game. It's really special.

"We'll probably have a couple of beers and relax together and we'll be getting dressed up which is good.

"I'm heading home tomorrow and I'll be straight back to working in the shop."