Guy Sebastian just pulled off the celebrity prank of the year.

Attention Jason Dundas: when pranking a friend on the Hamish & Andy show, please ensure you are the pranker and NOT the prankee.

The TV presenter learned this lesson the hard way on Monday afternoon when the legendary HIT Network hosts flipped the tables on him.

While the 34-year-old thought he was pranking The Voice judge Guy Sebastian about pretending to have a crush on coworker Iggy Azalea, Guy was actually in on the whole thing.

The result? Bloody hilarious.

“I’ve got something kind of random to ask you,” Jason began.

“So, how do I put this? You can say that this is totally whack, but I felt like there was a bit of a vibe with me and Iggy.

“I think she likes me and I kinda like her. So I’m not sure if it’s my place to go and ask her on a date, but I actually really like her.”

And this – THIS, my friends – is when Jason Dundas begins to look like he swallowed a lemon.

"Dude. Um. Dude something happened with me and Iggy which was really random," Guy answers.

"[It was] the last round of the auditions, because we all went out and then it was just me and Iggy in the lift and no joke she leaned in and like, went for a kiss.

"And I didn't really stop it straight away, like I haven't told Jules [wife], I haven't told my brother. So, sorry dude I just don't know."

Good guy Jason tries to rescue Guy's reputation with: "But you didn't... you didn't like do anything, right?"

"We had a bit of a pash, so it's sort of weird. Bro, please don't say anything, I can't have it get out," Guy replied, somehow without laughing, while Jason furiously motioned to Hamish Blake and Andy Lee to cut the recording.

But when Andy jumped in to add "Guy, sorry, it's Hamish and Andy here mate. We were just mucking around... it was Jason's idea," the jig was up.

"I feel like he's in on it," Jason said. "He's so in on it! I read the book about lie detecting, I can see you so hard."

Ah, what a classic.

You can watch the prank in full below.