After the Mullet finished their performance, they fell down on stage and the head of their costume completely fell off, revealing dark brown hair underneath.
Host Osher Günsberg rushed over to help hide the singer, and by some miracle, the celebrity managed to save their identity.
“I did not see a head at all you turned into a tortoise real quick,” Dave said.
The blunder sent fans into an absolute frenzy, with many taking to the comments under the clip to guess the identity of the character.
"Mullet is Dipper surely," one viewer wrote on Twitter, referring to former AFL star Berto "Dipper" DiPierdomenico.
"I think Mullet is Dave O'Neil, no idea why I think this but I do," another tweeted.
Meanwhile, another suggested: "The fish [Mullet] is Jimmy Barnes."
Radio host Chrissie Swan even chimed in, and said that she's already figured out who is actually under the Mullet mask.
Speaking on her radio show Chrissie, Sam & Browny about the latest season of The Masked Singer, she revealed her guess.
"Lindsey Lohan is not in it sadly, but the Mullet mask is in it and we've already guessed," she said. "It's Dylan Lewis! It's Dylan Lewis!"
She then confessed that it was anchor Dean 'Deano' Thomas who figured out Dylan Lewis is the one supposedly under the Mullet mask.
Despite all the speculation, as anyone who has watched the show knows, you can never be sure who is singing until the mask comes off.
What we do know is that Osher has returned as this year's host, while Dannii and Dave are joined by Urzila Carlson and Jackie O on the judging panel.