Katherine loves Peep Show, Star Stories, One Foot In The Grave, Pulling, League Of Gentlemen, Steptoe And Son, and Bruce Forsyth's The Generation Game.
In 2007, Katherine announced her engagement to fellow comedian Harry Peacock.
Katherine's mother teaches English at James Allen's Girls' School.
Katherine stars in a television advertisment for Maltesers.
She has also appeared several times on BBC Radio 4, including on Talking and Not Talking, Mouth Trap, with Katy Brand, and in The Odd Half Hour.
In 2008 Katherine contributed sketch characters to Katy Brand's ITV2 show, having been friends with Brand since Oxford.
When at the London Academy of Music and Dramatic Art she left to star in the play The Age of Consent.
Katherine met Chris O'Dowd, fellow The IT Crowd lead, for the first time at the London Academy of Music and Dramatic Art. They both left without completing their studies.
Katherine appeared on the London Stage in Hamption's new version of The Seagull in 2007. She appeared opposite Kristin Scott Thomas at the Royal Court.
Katherine: My best was me doing my Shakira to [Katy Brand's] Beyonce in a music video. That was a pleasure, great fun!
Katherine: Studio-based sitcoms have become synonymous with slightly dated stuff, and so many of the modern sitcoms like Gavin and Stacey and Pulling don't use a studio.
Katherine: (about filming The Old Guys) When I had to "cycle" down the steps they put me on a rickshaw and pulled me down because a stuntman did the actual cycling down them. Two men pulled me down and it turned out to be rather terrifying so my reaction when I say "I'm going to die" is most genuine.
Katherine: I'm going to get myself one of those, um, movable computers - what do you call them...? Laptops! I am bad. I still call my radio a wireless.
Katherine: People don't realise what a nice thing it is for an actor to go to a job where they know or like everybody, because you're so often having to do new beginnings, starting off on set with people you don't know, having to introduce yourself and make friends.
Katherine: I wish I'd done English, because anyone who's done that has this amazing reserve of knowledge about all sorts of literature. I can't remember anything, because I crammed it all. But obviously that shouldn't stop me from becoming prime Minister. If only they'd give me a chance.
Katherine: (about her character in Doc Martin) I've had to take a motorbike test because Pauline gets a motorbike, although I've decided not to pursue riding motorbikes. After they saw me on it, about 76 people said that I should consider not driving again - not just for my safety, but for the safety of others.
Katherine: I'm going to affect a transatlantic drawl when I've done my four months on Broadway.
Katherine: I always say I owe Lamda so much. It's about 10 grand.
Katherine: I've become one of those women who thrusts her engagement finger out all the time.