International superstar Katy Perry prancing around your kitchen, singing made-up ditties about your food and dipping her fingers in your sauce would be enough to send even the coolest chef into a spin.

But tonight's MasterChef immunity challenge is set to see one star absolutely wig out.

Mega fan Reece Hignell was reduced to a sweaty, shaky, giggly mess as a pregnant and full of beans Perry approached his workspace, leaving him speechless.

"Oh sh*t," he uttered, laughing and looking down at his workspace as the star introduced herself.

"I don't know how to talk, I don't know how to move, I'm just shutting down," Hignell told the camera, taking a deep breath.

Poh, Reynold, Sarah, Simon and Reece were battling it out for the immunity pin as the star's chaotic energy bowled into the kitchen.

The challenge - something "hot and cold" in honour of the show's theme song performed by Perry.

"Reece, The only thing is I don't love really fishy things, so anyone that's doing anything very fishy," Perry tells Hignell during their brief - and giggly chat.

"Well we're doing cake," he responded shyly.

"Oh I love a cake," Perry said, breaking into a bizarre dance.

"Ever since I became with child, I'm definitely into it.

"I have a serious allergy to gluten though … JK," the cheeky songstress added to an awe-struck Reece.

"Katy Perry is just like a goddess, she's just floating through the kitchen," the cook later said.

MasterChef: All Stars continues Sunday night from 7.30pm on Channel 10.