The presenter will introduce the show's highlights and eviction news alongside the housemates, who must do their best not to react or acknowledge her presence as part of this week's 'Ignore the Obvious' task.
Jedward are also set to enter the house today,
The 'X Factor' finalists - twins John and Edward Grimes - will perform their new single, 'All the Small Things' from the garden.
If the housemates are successful in the task, the group will win a luxury shopping budget and messages from home.
The housemates have already incurred at least one fail after Mario burst into tears after seeing his grandfather dressed as Father Christmas in the Diary Room, shortly after they received 11 fails in the first 11 minutes of the task.
The compound will be full of drama tonight, with a new housemate joining the group following The Departure of Laura earlier this week.
Graffiti artist Sam Pepper, 21, was one of the six hopefuls vying for a place in the house last week when the current housemates had to select three new people to join them.
He will now enter tonight, though he may face a rough welcome as he reportedly annoyed several contestants when they met during the audition process.
Meanwhile, the housemates thought there was a surprise eviction last night when Big Brother called the four nominated contestants - Ben, John James, Dave and Andrew - to the Diary Room at around 1.30am.
The group were concerned when only Ben, Dave and Andrew returned, wearing solemn expressions before the Christian minister buried his head in his hands and pretended to sob.
However, Dave soon started to laugh at his concerned housemates, admitting the prank had been John James' idea and he had not been evicted.
Josie said: "My heart sank then. He told you to do that? What a little w****r!"