It's so weird how Dobby became a sex symbol [Suttie played the geeky IT worker in Channel 4's long-running sitcom Peep Show until 2012.] I tried not to think too deeply about it, as it would have driven me mad, thinking, "I need to be a certain weight; I can't put on a pound!" I am quite similar to her, though: I used to play a lot of Dungeons & Dragons at school, but she's more hardcore than me.

I couldn't do stand-up for a few years because of 'Peep Show' When it aired, I was suddenly worried about headlining gigs advertised as "The IT girl from Peep Show". Would they see that I can play a part that's different from Dobby? I finally went back to Edinburgh, in 2011, with Pearl and Dave [about a socially inept man falling in love, which was adapted into an award-winning radio series, on Radio 4] and the worry passed.

I love writing about difficult relationships I love the awkwardness you get when people want something, but they can't say it. I love to watch that stuff, too – though it has to be about real feelings. It's why I love watching the American version of The Office. It's incredible.

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Little things become a big deal in small towns My mum used to write letters to me about things going on at home in Matlock [Derbyshire], and they were so funny that I started to use them on stage. She'd start with, "A funny thing happened at the fish shop…" One time she wrote that she was talking to a neighbour about the bad weather and her having this great big coat on and my mum said, "It's ridiculous!" The neighbour thought she meant her coat. When people get older and there's nothing to do till bridge in the evening, these things become important.

Knowing what others really think of you is a bad idea I'll never forget getting drunk on holiday with a friend when I was 14. She said, "Let's tell each other every bad thing anyone has ever said about the other." It was the worst game in the world; we both ended up really upset. That's why I don't Google myself: you want to see the good stuff but it's like playing Russian roulette.

Success has made me more private I always wanted to be an actress, but as a teenager I imagined acting meant courting the paparazzi and trying to get into the Groucho [Club] every night. But what's surprised me is how [after work] I just want to go home and cook. I don't think I've ever been "papped".

Social networking can be quite invasive If I'm not careful, 45 minutes will go by and I'll be blindly scrolling through people's profiles who I don't even know very well: it's a bit dangerous. My biggest online guilty pleasure is finding pictures of baby rabbits – there's a great one out there of a rabbit in a teacup; as far as guilty pleasures go, it's not as bad as taking heroin.

There's something magical about derelict houses I used to play in one near my home as a kid. So if I see one now it brings out this Freudian memory of childhood. I don't like ruins – you need to be able to walk along corridors, finding locked doors and think, "I'll get in there one day." There's something fairy-tale about it.

There's a human tendency to embellish I just think the character I portray in The A to Z of Mrs P [the eccentric London street-mapper Phyllis Pearsall], did it more than most; she'd take a fact then add a few colourful details. [Pearsall's claims that she got up at 5am every day to walk 3,000 miles, along 23,000 streets, until she'd completed the A to Z, have been met with scepticism.]

Isy Suttie, 35, will be starring in the stage musical 'The A to Z of Mrs P' at the Southwark Playhouse, London SE1, from Friday