When Karl met Heidi: Supermodel pranks TODAY host with yodelling gag

Supermodel Heidi Klum and TODAY Show co-host Karl Stefanovic pulled no punches when they went head-to-head on this morning's show.

The German-born Klum has returned to Australia for the first time in 15 years to celebrate her launch of a new underwear line for Intimates.

Speaking with Karl on Australia Day, the supermodel tried her hand at some classic Australianisms.

"Mate, let's go and put a shrimp on the barbie, love," she said, trying her hand at an Aussie accent.

But Karl was unimpressed.

"That was woeful," he laughed.

Klum kept at it, however, as she tried a few staples of Australian cuisine, including Vegemite toast, a sausage roll, a Cherry Ripe and a Tim Tam.

She proclaimed the Cherry Ripe to be "real noice", in an accent that would not have been out of place on Kath and Kim.

Klum later got her own back on Karl as she tried teaching him to yodel.

"Try a little harder," she said after his first effort.

After she demonstrated her own impressive set of pipes, an awed Karl asked how long she'd been yodelling for.

"I don't really know how to yodel," Klum admitted, sending Karl into fits of laughter.