McCall is one of the judges on the hit ITV contest which sees mystery famous people singing dressed in elaborate costumes and known only by their character's name, before being unmasked as they are eliminated.
The Masked Singer final airs tonight (Saturday) and McCall told The Sun that everyone was desperate to find out who was behind the masks of finalists Mushroom, Panda and Robobunny.
Saying that her most used emoji over recent months had been the shrugging person as she fielded constant Masked Singer guesses, McCall added: "Non-stop, people ask me, friends ask me. I was in Tesco today and someone tried to trick me into saying something.
"They go, ‘Of course Panda is so and so’ and I go, ‘You’re not going to do it that easily. I’m not even going to give you a hint you might be right!’ If you find out before the show and you didn’t just guess it, it ruins it. That is the joy of the show.
"We’re like Official Secrets Act-trained — we’ve signed, like, an NDA (non-disclosure agreement) and legally we can’t discuss it."
Each episode, the judges and viewers are offered more clues to the characters' real identities as they make cryptic comments about their lives.
Fans of the show love posting their guesses on Twitter and McCall admitted that just a couple of episodes into series three, someone had "guessed virtually everyone correctly" - although, of course, she didn't reveal who it was.
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Viewers are convinced that Mushroom is Charlotte Church and Robobunny is Mark Feehily, although Panda's identity has people slightly more confused.
McCall judges alongside Mo Gilligan, Rita Ora and Jonathan Ross, and tonight they will reveal the series three champion who will join the list of previous show winners Nicola Roberts and Joss Stone.
The Masked Singer final airs tonight at 7pm on ITV.
Watch: Ken Jeong and Robin Thicke walk off Masked Singer US in protest at contestant