The seven children of Mr Brown are so naughty and out-of-control that every nanny they have runs screaming from their house - until Nanny McPhee arrives that is!
The not very pretty Nanny McPhee
She appears from nowhere one stormy night and sets about working her magic on the children - despite their best efforts to make her job as hard as possible...
Newsround met three of the children who star in Nanny McPhee: 13-year-old Eliza who plays Tora, 11-year-old Raphael who plays Eric and nine-year-old Sam who plays Sebastian.
Read on to find out what it was like being in the film.
The Brown children may well be the naughtiest children ever - so are you anything like the character you play?
Raphael: Well I can't really say that but I think some people would!
Eliza: I'm not hugely like my character I have to say, but I think it is always good experience playing roles that are completely opposite to what you're like.
Sam: I'm almost the same as Sebastian because I like stealing food from the cupboard like he does!
Did you find it easy or hard to play the part?
Tora, right, with her father and sister
Sam: Very easy!
Eliza: After getting to know your character as a person I think it is easier to actually become them, rather than just being like them.
Raphael: It wasn't actually that easy for me because I had to act as if I was a 40-year-old professor trapped in the body of a seven-year-old boy and I'm not really like that.
I just put on a voice like I'm cleverer than everyone else.
How did you get the part?
Raphael: My mum's friend is an agent so she spotted me and my brother.
Eliza: The agency came up with the audition and there were so many kids we had workshops with lots of children. It was a long audition process - we went through eight or nine before they were able to put the family together.
Sam: I got it through an agent.
How did you behave while you were on set?
Eliza: Well there was a bit of teasing and stuff but we weren't that naughty really.
Sam: I was - when doing the beach scene I kept stealing doughnuts and the props men weren't very happy as they weren't there for the next scene!
What was it like working so closely with so many other children?
Eric getting up to mischief
Raphael: It was actually pretty good because there were some like me who were new to the filming world and then there were experienced ones like Eliza and Simon.
Eliza: We got on really well because we are all such different ages and played such different characters. So it was like we were one big family.
Did you learn anything from your co-stars?
Eliza: Working so closely with Emma Thompson you are forever learning and getting tips.
As Emma wrote the script she had an idea in her mind what the characters would be like and she really helped us along the way to build up our experience of the characters.
There are pigs, chickens, dogs, a donkey and a spider in the film - what was it like working with so many animals?
Raphael: I had to hold the spider and I felt very bad about that. I have a fear of them which I didn't manage to overcome - I just had to stand very still and get on with it.
Sam: In one bit we were pulling the rope of a donkey and the prop man let go - we didn't know he was going to so we fell down! He did it on purpose though as he wanted to catch us by surprise so it would look realistic.
What did you get up to while you were waiting on set?
Raphael: We had to have three hours school tutoring a day.
Eliza: We also had a chill-out room for our breaks with bean bags, play stations and TVs.
What was the best bit about making Nanny McPhee?
Sebastian wreaking havoc in the kitchen
Raphael: The money!
Eliza: Meeting all the really experienced actors and actresses. The whole thing was a really fantastic experience.
Sam: Everything - like getting to act and getting paid to do it.
It means I have extra money for when I'm an adult so I will be able to buy my own house.
Would you like to continue acting?
Raphael: Not really no.
Eliza: I would love to carry on acting.
Sam: Yes - I want to be in Harry Potter! I could play one of the new characters from her next books but if I could play anyone it would be Ron - he's my favourite.
Have your lives changed since getting the part?
Sam: Not really - it's just the same as being an ordinary person.
Eliza: Not at all - I go home and I'm told I have to tidy my room and go to school - doing a film doesn't make anyone any more special.