The Greatest Dancer captain Cheryl brought along her final team, Froback to appear on the show.
Their challenge this week was “social network” which prompted Cheryl to make some calls to her celebrity friends.
As the group began dancing, a Robbie Williams song played, prompting a huge reaction from the audience.
Eventually the screen behind the group showed off a clip of Robbie sending his best regards.
This happened once again with Perrie Edwards once a Little Mix song finished playing.
But viewers were left the most shocked when Liam Payne’s song “Strip That Down” started.
Liam then appeared in a clip behind Frobacks, leaving viewers a little stunned.
The clip saw Liam say to Cheryl: “Chez can you put the Frobacks on please?”
Cheryl pointed her phone towards the group, prompting Liam to say: “Hey man, you guys are killing it!
“I’d love you to teach me some tricks some time so make sure you get my number off Chez, okay?”
Viewers began writing on Twitter: “#GreatestDancer I said Liam would be included as a joke THEN HE POPS UP as if lol.”
Another wrote: “#Cheryl face when Liam can up… awkward #GreatestDancer.”
“Cheryls face wen Liam called was amazing fp,” one added.
One said: “@LiamPayne on #greatestdancer was the highlight of the performance tbh @GreatDancerTV.”
The other dance captains didn’t exactly enjoy Cheryl’s choice of challenge props, however.
Both Oti Mabuse and Matthew Morrison believed the FaceTime clips distracted from the dancing.
Matthew announced: “It was distracting and it took away from the dance.”
Earlier on in the show Cheryl and Matthew clashed over some feedback.
Matthew’s act, Prospect Fraternity, performed with a number of tables for their challenge.
But Cheryl quickly gave some feedback, saying: “And, the only thing I would say is – and this is a note for Matthew…
“It’s the table thing. It has been done before.”
Unfortunately for Matthew, Oti agreed with Cheryl, leaving him to worry for his acts’ safety.
The Greatest Dancer continues Saturday at 7.35pm on BBC One.