Karl Stefanovic is making his primetime hosting debut on 2GB and 4BC radio, filling in on The Steve Price Show.

The TV star has done a Steven Bradbury and come in as the last man standing, with Alan Jones off sick, Steve taking over breakfast and Deb Knight unavailable.

As such, Ray took it upon himself to give his old mate some advice… live on-air.

It started with how to tell the time correctly and ended with two ripping into each other at any opportunity.

The pair also went on to discuss Ray’s bizarre new relationship with fellow radio host Kyle Sandilands.

“I’m now performing on his program for watermelon juice,” jokes Ray.

“It’s comment for watermelon juice!”

Click PLAY below to hear the full chat