The show's panel - Davina McCall, Jonathan Ross, Maya Jama and guest judge Danny Jones - were left in awe when Samantha took off their mask to finally confirm their identity.
A second wrote: "I haven't a clue who she is," while a third echoed: "Very enjoyable But sadly, I don't attend musical theatre in London so I had no idea who Samantha was Gregory Porter and Marti Pellow were amazing though!".
Although Samantha is best known for her role on stage as Elsa in acclaimed adaption of Frozen, some watching at home had "no idea" who she was.
Finishing a close runner-up to Samantha was Dressed Crab who turned out to be soul and jazz star Gregory Porter.
Fans of the ITV guessing game were stunned when West End's leading lady, Samantha Barks was behind the costume.
