Sam Wollaston

I like to imagine Julia Davis and Jessica Hynes, who co-wrote and co-star in Lizzie and Sarah (BBC2, Saturday), sitting down together to create it. Hell, it must have been fun.

"We can't get away with that, can we Jessica?"

"Oh go on Julia. So Michael will put a pillow over my head so he doesn't have to look at me when we're having sex. And I'll almost suffocate. Then, when he's done his business, I'll say thank you, really meekly, trying to hide my tears."

"Ha ha ha, brilliant. And my husband John can have sex with the obese Brazilian au pair - pumping away loudly, enthusiastically and frequently, all over the house and in full view of everyone. I'll clear up after them, pretend it's not happening, play Boggle and make toasties . . . "

We know about Julia Davis's inappropriateness from the wonderful Nighty Night. But here, with her new partner in crime, she's cranked things up - or plumbed new depths - to a whole new level of excruciating. Ouch, it's painful - it has you wincing and squirming, clenching and screaming inside. Then exploding with laughter. Because it is very, very funny.

It's not just about shocking, though, and getting away with things (an awful lot of things, it must be said - 11.45pm is really the only time this could possibly have gone out). Lizzie and Sarah is also beautifully observed. It is far-fetched, but not that far-fetched. This is not a million miles away from stuff that goes on in pretty much every family (infidelity, ageing, insensitivity, cruelty, Boggle). And it's this - the recognition and familiarity - that makes it both so painful and so funny. In fact, when Lizzie and Sarah stop being walked all over, go postal and start to take revenge with a gun, it becomes less successful, I think. Because suddenly it's less believable. Still funny, just not so painfully so.

Anyway, it's a treat - brave and hilarious. With brilliant performances, too, particularly from Jessica Hynes (who, along with Julia Davis, plays a 16-year-old as well as a 56-year-old). It would be criminal if this pilot wasn't turned into a series - though, with a large percentage of the characters now dead on the floor, there may be some logistical issues to sort out. No worries, Davis and Hynes can just get together and dream up some more. I'd like to meet anyone they come up with.

If it was too late and you missed it (maybe you were in bed with a pillow over your head), go and watch Lizzie and Sarah on iPlayer. And if you did see it, watch it again. You'll notice things you missed first time round, like the boobs drawn on the zeros in 2009 in the poster for Vicki's memorial concert. "Vicki Bobin, 'she fell asleep with angels', 1993-2009" (with boobs). Vicki was run over by her own pervy father, who was distracted by her friends in their netball kit. See what I mean about the inappropriateness?

Episode two of The Persuasionists (BBC2) did not reward the theory that this new sitcom needed time to bed in. It's set in an advertising agency and features a talented cast (Adam Buxton, Simon Farnaby, Daisy Haggard) you have probably seen being funny in other things, but if you laughed at this, I'd like to try a handful of whatever pills you're on. Actually, I did laugh once, when a character tried to encapsulate Australian culture with the words "Have you ever worn shorts to a funeral?" but, had I not been watching in a professional capacity, I would have switched over long before that point. It's hard to locate exactly what went wrong with this project, so I'm recording a verdict of death by misadventure.

Right, that's the froth dealt with. Now to the espresso underneath. With a glass of Veuve Clicquot and a line of coke on the side. Because Material Girl (BBC1), an important new drama set in the world of fashion, takes on the ­altogether more profound question: what to wear? OK, it's silly and deeply shallow. It's also gorgeous, fizzy, bitchy, self-indulgent, obviously bad for you but dangerously addictive. Careful, Material Girl could become a habit.

Dervla Kirwan makes a splendid queen bitch evil designer with no talent but an impressive Rolodex. Being ­Human's lovely Lenora Crichlow is again lovely as Ali, the talented young designer, who's tottering in five-inch heels along the thin line between the real world and fashion nonsense. Only the hunk is wrong - too puppyish and doey-eyed to be a hunk, I think. And since when did motorcycle couriers ride Harley-Davidsons?

It's part of the Babylon franchise, based on the writing of Imogen ­Edwards-Jones. This is better than ­Hotel Babylon though - simply more fun. As usual, IE-J wrote her book with "Anonymous", an insider from the world in which it's set. Unfortunately, although I understand chaos theory perfectly, I know very little about ­fashion, so can't ­comment on its veracity. But I know a woman who understands fashion well, my own insider - let's just call her Guardian fashion editor Jess Cartner-Morley.

The daft, post-show, backstage ­"Darling, you are a fashion goddess" conversations between the celebrity and the designer are spot on, says JC-M. Plus the brash, very London supermodel, and the slimy Eurotrash ­business partner in the turtle neck - right again, those people are real.

Obviously a lot of old fashion cliches are dragged out, some of which JC-M could have done without, such as the scene in the shoe shop where Ali sells her soul for a nice pair of shoes: Jess is so over that scene, she's seen it about 5,000 times, come aaaawn. And where it's just plain wrong, she says, is when the baddie journalist demands sexual favours of a GIRL - very unlikely. The men in fashion really are gay. Oh, and she likes it. So I was right about that.

From the title, you'd expect it to be a channel Five documentary, but The Fattest Man in Britain (ITV1, Sunday) is actually a drama, co-written by Caroline Aherne. Timothy Spall, looking quite at home in a fat suit, plays Georgie, a good-natured human bouncy castle in Rochdale. But the star is Bobby Ball, who plays Maurice, his agent. Maurice takes foreigners on guided tours of Georgie, for £11.50. It's in his interest to keep Georgie as big as possible. So he feeds him up, like a goose, for foie gras.

Some of the dialogue has a nice, natural Royle Family feel to it. But it's a bit silly really. And as sugary as one of the pop tarts Georgie keeps popping. "That's why this title is so important to me, Amy," he says to the nice girl who's come to live with him. "The Fattest Man in Britain. Because if I'm not the fattest, I'm just a fat man. Just a big fat man sat in his chair."

"You've already got a title Georgie: you're My Friend."

Pass the sick bag will you. And give that man a gastric band.

Here, in Russell Brand: Skinned (Channel 4), is another faintly ridic-ulous man. He's being interviewed, rather well, by Frank Skinner, although, to be fair, Frank doesn't have to work hard. It just comes pouring out: drugs (again - shut up about the drugs), the women, Sachsgate (he's both sorry and not sorry), ambition. And it's very good, because Russell Brand is very good - funny, clever, quick, eloquent (he knows how to use words like dichotomy and caveat). Sometimes you have to marvel at the man.

I don't love him, though, wouldn't get into a hot tub with him (very happy to with Frank Skinner, however). Maybe it doesn't matter: you don't need to love someone for them to make you laugh. It's probably for the same reason that lots of men don't love him: he's funnier and more attractive than we are, and he's going to mate with our women. But there's more to it. In spite of his chattiness, his tactile rubberiness, there's something cold about him. Look into his eyes. He's a lizard, that's what he is.

There's only one way to get through Big Top

There's only one way to get through Big Top - by playing Guess the Gag, says Sam Wollaston.

"Just because Stephen Hawking, a famously disabled spastic, created his theories of black holes and the boundary conditions of the universe, whilst sitting in his wheelchair, it doesn't mean that you will be able to," says Jonty de Wolfe (comedy name!), vice chancellor of Kirke University, to a young man in a wheelchair.

Ah, I see, Campus (Channel 4) is taking that path: the offensive one. There's nothing wrong with that; offence can be good, if done artfully. There's plenty of it here - Jonty's bigotry and English literature lecturer Matt Beer's (comedy name, like beer mat, but the other way round!) sex pesting. There is talk of rape by pigs, and odd-shaped anal cavities that lead to odd-shaped stools. I'm just not convinced it is being done very artfully. It seems more like offence for the sake of offence. Compare it with the beautifully crafted filth of Malcolm Tucker in The Thick of It. If he is the Michelangelo of offence, this is Rolf Harris.

These Comedy Showcases are a great idea - pilots, which do or don't get turned into a series. Plus One came from it, and Free Agents. I'd put this one in the "don't" pile. It's also very obviously trying to be Green Wing, but relocated to a university. It looks like Green Wing, sounds like it, and adopts some of its tricks and surrealisms. But - and it's a big but, especially in a comedy - I'm not laughing very much. And I was, a lot, in Green Wing. That was original, and surprising, more subtle I think ... Hell, I don't know why something is funny, and something else isn't. They just are, OK?

Like musical jokes. Never, ever funny, agreed? And yet, the best sketch in The Armstrong and Miller Show (BBC1) is the one where Armstrong is tinkling away on the piano in an Edwardian drawing room. Then he suddenly and seamlessly segues from Vivaldi or whatever into Gay Bar by Electric Six. Which makes the ladies faint. Funny, eh? Comedy, it's a mystery. Or possibly just pot luck.

Nicola Murray is the new Secretary of State for the Department of Social Affairs and Citizenship in The Thick Of It (BBC2, Saturday). Sounds important; it isn't. If she'd said no, the only other candidate was Malcolm Tucker's left bollock with a smiley face drawn on it.

It's really just a job title, not a job, but Nicola doesn't know that yet, and has ideas about things like social mobility. She's like the new girl at school - trying to work out who to make friends with, where to fit in. The other kids - Ollie and Glenn and Terri - circle suspiciously. They sneak on each other, and lie, and gang up.

Then Malcolm, the big playground bully, shows up. He opens his enormous mouth as wide as it will go and vomits out a seemingly never-ending torrent of verbal abuse. If you're reading pre-watershed, or you're a child, you must stop reading right now, because I've put some of Malcolm's bad words in. It's hard not to - they're such a big part of The Thick Of It. "You're a fucking human dart board, and Eric fucking Bristow's on the oche throwing a million darts made of shit right at you," he splutters to Nicola. "Jesus Christ, you're a fucking omni-shambles, that's what you are . . . "

And so it goes. It's filthy, and yet it's so beautifully crafted and so perfectly delivered, it's almost as if Malcolm's actually turned swearing into art. And omni-shambles - isn't that lovely?

Nicola (played by the funny and brilliant Rebecca Front, a welcome addition) has a brave attempt at taking Malcolm on at his own game. She tells him her daughter is on heroin, "although she has cut down since getting pregnant by that Nigerian people smuggler, cos the track marks would have affected her porn career". But it's futile, like taking on Lionel Messi - Lionel fucking Messi - at football. And she ends up sacrificing her daughter's future for Malcom's party line.

I want to work at the Department of Social Affairs and Citizenship. I mean, it's lovely here at the Guardian - looking around, I'm surrounded by intelligent and mostly reasonable people, tapping away on their keyboards. There's some good-natured banter, a few jokes, a bit of gentle back-stabbing. But nothing like what goes on in The Thick Of It. I want the blistering bickering and the bullying, the full-on playground experience, I want to be bollocked by Malcolm Tucker.

It is a brilliant performance by Peter Capaldi, and by Front, by all of them. But the real genius is in the writing. It's so out there and yet totally believable, so polished, so well observed, right down to the smallest details. That Nicola Murray stands in front of a campaign poster for Liam Bentley so that it reads IAM BENT right by her head is funny; that it immediately appears on YouTube is funnier still, and that the YouTube footage is intercut with random bits from Family Guy is best of all. "Why do people fucking do that on YouTube, it's not even funny," says the hapless Nicola. Yes it is. At least she's learning the language.

The movie - In The Loop - was good, but this is better. The Thick Of It works best like this, in short, rude blasts. What's going to happen when the Tories get in, I'm wondering (and worrying). Does The Thick Of It work in opposition?

In Peep Show, Jeremy and Mark venture outdoors - to the park for a picnic to celebrate Elena and Gail's forthcoming nuptials, and later, to the country. I'm not sure Mark and Jeremy really belong outside; certainly not in the countryside.

It's a beautiful finale, though, with all the disappointment, inappropriate-ness and sorry truths you would have wished for. And wonderful, wonderful lines. This series has been an absolute treat, the best yet. Can it really be over so soon? I guess there's something appropriate about the end of Peep Show coming too soon. But where are the chuckles going to come from now? Ah, The Thick of It starts tonight, that's where.