The former Girls Aloud star called in a few showbiz favours to help her act Frobacks with their latest performance on Saturday’s show.
With their routine themed around social media, the dance troupe received FaceTime calls from some contacts in Cheryl’s phonebook during the performance, one of which was her ex Liam.
Cheryl picked up the “call”, which was actually pre-recorded, with Liam asking: “Chez, can you put the Frobacks on, please?”
Cheryl - who serves as a dance captain on the show - rolled her eyes at the request, before turning her phone to face the stage.
Liam continued: “Hey man, you guys are killing it.
“I’d love you teach me those tricks some time, so make sure you get my number off Chez, OK?”
The pair claimed that the group having to stop dancing to receive the calls disrupted the energy of the performance.
Cheryl and Liam announced they had split last July after two years together.
However, they have remained friendly for the sake of their son Bear, who is nearly two.
In January, Cheryl revealed that she and Liam spent Christmas together, telling The Sun: “There’s no animosity whatsoever. In fact, Liam spent Christmas Day with us. He cooked the turkey and everything at our home. His family came on the 23rd, and then he was in the house before I woke up on Christmas Day.
“It was lovely and things with us are great, which is lucky, really, because I have to listen to his songs 55,000 times a day. Bear’s got an obsession with the beginning of ‘Familiar’. We have to rewind it and play it all over again.”