The US reality stars - who entered the basement area of the house last night (January 3) - were chosen by their fellow housemates to carry out the assignment of unblocking the clogged water pipes.
The couple instead decided to go on strike, and told Big Brother that they would not go through with the task.
Ryan Moloney - who plays Jarrod 'Toadfish' Rebecchi in Australian soap Neighbours - then decided to step up and take on the challenge, which would return hot water to the celebrities living in the 'luxury' house upstairs.
Moloney made his way to the pipes outside in the garden as both groups of housemates watched on screens.
"I guess [Big Brother producers] built this whole thing and they had to have a scene but I think it would have been funnier if they'd had cold water," said Pratt as he looked on.
As his wife agreed, Pratt added: "That is one obnoxious crew. I don't want to go near those people."
The housemates living in luxury were not afraid to show their mutual dislike of the Pratts as the situation played out.
"Nobody when asked to do a chore on Big Brother should turn it down whatever it is," said former model and newly promoted upstairs resident Paula Hamilton.
The rest of the group then continued to heap praise on Moloney, with even Montag admitting that the actor "has like the greatest attitude ever".
Celebrity Big Brother airs tonight at 9pm on Channel 5.