The public's favourite performance was Garraway and Arnold's rendition of 'Born To Handjive' from Grease, which judge Paddy McGuinness had described as "absolutely fantastic".
"Did I just win a dance show?" Garraway laughed. "This means we've got to do it again!"
Judges McGuinness, Miranda Hart and Kelly Brook then had to choose between Sam and Mark's performance of Wham's 'Wake Me Up Before You Go Go' and Debra Stephenson's dance to 'Smooth Criminal'.
Hart opted to save Stephenson, but McGuinness said he was choosing to keep Sam and Mark for "comedy reasons". Brook had the deciding vote and complained that the decision was "hard". However, she eventually chose to keep Stephenson.
Other acts who performed this week were the boxers Carl Froch, Johnny Nelson, Tony Jeffries and Duke McKenzie, comedian Shappi Khorsandi, and the Weathergirls and Michael Fish.
Garraway and Arnold and Stephenson will now join Katy Brand and Rufus Hound in the final of the show.
Let's Dance For Sport Relief continues next Saturday at 7.15pm on BBC One.