Rove McManus' odd behaviour on The Project last week was all Sam Frost's fault.

If you were watching Channel 10’s The Project last Friday night, you might have noticed guest host Rove McManus went… well, a little off the deep end.

During the episode, McManus dropped a number of words and phrases into the conversation that made the usually composed host come across like the “cool dad” of every teen’s nightmares.

However, during his morning radio show Rove and Sam today McManus’ unusual turn of speech has been revealed to be a big joke.

As co-host Sam Frost explained, she had challenged McManus to use a list of certain phrases during his time on The Project.

“I thought the very least you could do to show your loyalty to me is slip in a few words,” she said.

“I wanted you to throw in ‘chitty chat’, ‘hectic’, ‘guys guys guys’, ‘delightful human’, ‘me scusi’ ... and ‘mouldy pits’ because of our executive producer [Alex Spurway] who has moudly pits.”

McManus took up the challenge and did a bloody good job, even managing to say "me scusi" and "me absolute scusi" without somebody throwing a shoe.

Listen: Mia Freedman interviews Sam Frost on her No Filter podcast. (Post continues after audio.)

His execution was not completely perfect, however — one canny viewer did catch on to the hectic chitty chat.

"Does Rove usually act like a 12-yr-old boy or is this some new thing?" they tweeted.

Guys, guys, guys. We loved it.

Feature image via Instagram/@RoveandSam.