THE One Show's Alex Jones barked 'no, stop!' at Caroline Quentin after she dropped major Comic Relief spoilers.
Caroline, 60, appeared on Wednesday's edition of the BBC One show to talk about the challenge she will be taking on for the charity event.
Caroline and a number of other comedians including Jennifer Saunders and Alex Brooker will try and sing at the opera for the first time on live TV on Friday.
Alex, 44, explained to viewers: "On Friday night, you and another four comedians have agreed - I mean what Richard Curtis gets you to do is unbelievable sometimes - to sing an operatic aria, live on BBC One.”
Caroline, who was speaking via video link from home confirmed that was correct and Alex added: "And you only have 24 hours to rehearse this."
Caroline continued: "The challenge is that we all have 24 hours to learn to sing an operatic aria.
“We are assisted by the British National Opera, their orchestra and their chorus.
Caroline started to laugh at the ludicrous nature of the task ahead and said: "And they have given us - I’m slightly hysterical can you tell? They have given us 24 hours to sing…”
But as Caroline started to reveal the name of the song she would be trying to sing, Alex cut her off.
She cried: "“No! Stop, stop!” while her co-host Michael Ball also said: "No, no, no."
Alex said: "Let’s do a reveal, because it is quite up there. This is the song they’ll attempt to belt out..."
They then showed a clip of the five comedians looking gobsmacked in a theatre as they heard the song they would be attempting to sing.
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The music was Nessun Dorma - or Let No One Sleep - from Giacomo Puccini's opera Turando and Caroline was seen waving goodbye and getting up from her seat in the clip.
Back in the studio, Michael, 58, said: "I sense a little bit of reservation there about the song choice. I don’t know if I’m right.”
Caroline replied: “I honestly truthfully thought they would give us something in English, which would have been a start, I can order an ice cream in Italian, that’s the size of it and also that is a big sing isn’t it?”
The One Show airs weeknights at 7pm on BBC One. Comic Relief's Red Nose Day takes place on Friday, March 19.