WHAT happened to Karl?

That's what Today viewers wanted to know after the co-host of the Channel Nine breakfast show disappeared during the last hour of the show.

Stefanovic was last seen on air at 7.40am and then went missing, leaving Richard Wilkins and Tim Gilbert to pick up the slack and co-host the remainder of the show alongside Lisa Wilkinson.

There was no explanation offered as to why Stefanovic wasn't around for the last hour of the show and fans were left scratching their heads.

"Why did Karl disappear halfway through this morning's show?" one fan wrote on Today's Facebook page.

"Where are you Karl?" asked another, "you seemed to have disappeared off screen".

So what exactly happened?

News.com.au put the question to Channel Nine and a spokesperson told us: "Karl is on leave for the next few days. He will be back on air at the end of next week. Ben Fordham will be filling in for him."

Hmmm ... doesn't really answer the question, does it?

Karl Stefanovic last had a week off back in April when he was spotted holidaying in Mexico with his girlfriend Jasmine Yarbrough and her family.