Miranda Hart is to take on five mystery challenges for Comic Relief.
The 'Call the Midwife' star is to undertake 'Miranda's Mad March', which will see her tackle a series of tasks in different cities for The BT Red Nose Challenge.
The daily task will be revealed on Chris Evans' BBC Radio 2 Breakfast Show, and she will have hours to complete the challenge, with the results broadcast on 'The One Show'.
Miranda - whose first task will take place in Newcastle on March 11 and the final one in London on Red Nose Day, March 15 - said: "I hope the good people at Comic Relief aren't too hard on me and that the British public get behind me to raise heaps of cash for Red Nose Day."
Meanwhile, the 40-year-old star admitted she didn't realise her 'Call the Midwife' character Chummy's latest storyline was meant to be a secret.
The midwife returns from Africa, where she has spent six months doing missionary work with husband PC Noakes (Ben Caplan), pregnant and Miranda couldn't help but blab the twist to her pals.
She admitted: "I've been telling all my friends, I didn't realise it was a big secret. Oops."
And the comic star was shocked to find herself shedding a tear after her own birth scenes.
She told the Daily Mirror newspaper: "We've just done the scene where I meet my little son. I started welling up, just quite naturally. It was the first time I'd thought, 'Wow, it must be amazing to have your own child'."