Sheridan Smith says her character Sheila is like a classic pantomime villain.

How did you get involved in Ratburger?

I worked with David Walliams on Mr Stink. I also played an evil mother in that - am I being typecast? In David's shows, I always look a complete fool - which he loves, and I love, too! I love sending myself up. So when David said, "Would you like to play the part of Sheila in Ratburger?" I jumped at the chance!

For you, this is just the latest of many fruitful collaborations with David, isn't it?

Absolutely. We have a great relationship. We love working together. I worked with David on a West End production of A Midsummer Night's Dream, and when he was making his sketch show, Walliams & Friend, he got me in for an episode. I played Barbie, a cruise ship singer and a Carry On character. I had a ball. Working with David on Ratburger has been great fun, too.

Tell us about Sheila...

She's a baddie. She's like a classic pantomime villain. She's not a very nice character, but she is a lot of fun to play. She loves the gruesomeness of it all, and asks Burt, "Can I come up and watch the rats going into the mincer?" I'm actually being very polite - Sheila is an absolute horror!

Talk us through her relationship with Burt...

Sheila falls head over heels in love with Burt. I don't know what attracts her to him, but they go on a date. In the show, we have this terrific montage of film references from the Dirty Dancing lift to the rude scene from When Harry Met Sally to the Ghost moment with a burger. Doing those scenes, it was quite hard to keep a straight face.

Is Sheila also quite greedy?

Definitely. All she does is eat prawn cocktail crisps. I had 10 packets yesterday! I have to wear padding. It's so funny!

Sheila is quite a sight, isn't she?

Yes, but I love that. It's great to have no vanity. You have to just let it all out. I'd much rather be a silly character and have fun. The fun part is when you arrive and see your character's outfit - that cracks me up already.

When I went to the read-through for Ratburger, I had pink hair and the producers said, "We love that - let's keep it." Basically, I'm Sheila - don't worry, I'm not!

Is your interpretation of Sheila inspired by anyone?

Ratburger is set up north, but I'm playing Sheila as a cockney. It makes me feel different. She's like Phil Mitchell in drag! I'm also trying to channel Waynetta Slob because Kathy Burke is my hero.

They say that you should never work with animals. So how have you found it performing with the rats?

Actually, I've been fine with them. They're so good. They're very well trained. They have been incredible - they're real scene-stealers!

What is your view of David's novels?

He is a genius - it scares me! He's like a modern-day Roald Dahl. My goddaughters adore him. His writing is dark and twisted and fun and has heart. David always writes so well about children. He's a big kid himself - like we all want to be. He is great with children - he gets them. But don't tell him I said so - he'll get a big head!

Why do you think Ratburger will make brilliant Christmas viewing?

Because it's a real family show. Kids will love it, but there is also humour in it for adults - that's why we are having so much fun making it. When David does these one-off dramas, it feels like an event. It's a great opportunity for us to get together.

What do you hope that viewers will take away from Ratburger?

It will make kids scream, but David's writing is also full of heart - he always brings a tear to the eye at the end. This story is all about love. What's the moral of the story? It's about being true to yourself.

You also have a tremendous reputation as a serious actress. Do you prefer comedy or drama?

I love both. I love doing dramas with passion and pathos and emotion, but I also love doing things like Ratburger where you can just have a laugh. A change is as good as a rest. Making Ratburger has been so much fun, it's not really like work at all!