Antony Costa, Simon Webbe and Duncan James walked into the house singing one of the group's classic hits, with Duncan even giving Luisa Zissman a cheeky kiss on the lips.
Sam Faiers also got a surprise when her mum appeared.
But the special appearances were all part of a task today where the remaining Celebrity Big Brother housemates must ignore the obvious
Big Brother has installed a giant grandfather clock in the house and the group freeze whenever they hear the bell toll, no matter what is happening around them.
Big Brother will be sending a number of surprises into the house whilst the celebrities are frozen, which they must ignore in order to win the task.
Housemates are only allowed to move again when they hear the second clock toll.
The task will air on tomorrow night's highlights show on Channel 5.
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