The off-hand, let's-just-have-fun style of `Light Lunch' probably takes an hour in make-up to achieve. They swan in dressed to the nines and perfectly coiffed and then have to be reverse-engineered into a condition of studenty scruffiness.

The two presenters of Light Lunch, Channel 4's lunchtime chat- show, do not possess the conventional gloss of daytime speakerines - in fact they frequently look as if their alarm failed to go off and they had to skip the usual ablutions and chuck on the first garments that came to hand. The look isn't grubby, exactly (they keep that for the jokey banter), but it is calculatedly rumpled and informal. This is so much in keeping with the off-hand, let's-just-have-fun style of the programme that it probably takes an hour in make-up to achieve it. They swan in dressed to the nines and perfectly coiffed and then have to be reverse- engineered into a condition of studenty scruffiness.

They apparently have quite a large student following and you can see that their rapid, polysyllabic patter might appeal to that constituency - particularly because of the thick insulating layer of irony with which every single remark is lagged (even the body language has inverted quotation marks around it). The show begins with someone cooking a meal and ends with celebrities eating it, in a daytime telly version of the Last Supper - that is, they all line up on one side of a long table facing the audience. There are terrible jokes ("I say Mel, have you seen Oliver Twist?" "No, but I've seen him doing the hokey-cokey.") and lots of lubricious puns ("They're mean, they're lean and I'm not talking beef," someone said, introducing the band. "They only need to be lightly tossed to release their juices") but, because nothing at all is meant seriously, nothing serious can go wrong - if a joke fails they just do a little schtick about how embarrassed they are. It is all quite polished - in its studiously unpolished way - but there is also something grating about its manner. I couldn't put my finger on what it was exactly until a member of the audience revealed that her packed lunch consisted of cheesy peas - a reference to a Fast Show sketch. Then it finally came to me - with their nudging innuendo and funny pronunciations ("aminals" for animals and "kwich" for quiche), Mel Giedroyc and Sue Perkins are distant female cousins of Colin Hunt, the Fast Show's egregious office zany.

Expanding Pictures, BBC2's series of short art films, might be described as video installations by stealth; like the purloined letter in the Edgar Allen Poe story, they have been placed in the last place you would look for such a thing - your dull, reliable telly. And there they have a rather refreshing effect, because their opacity is so much at odds with the anxious clarity of everything that surrounds them. Last night's wasn't the strongest in the series - a speeded-up love affair which compressed the arc of infatuation and disappointment into a collage of soundbites and fast-cut images. But the best have played with the possibilities of the technology in an almost childlike manner - enjoying the ease with which film, notionally the most realistic of mediums, can be made to unbalance the viewer. Lip-synching is popular, as in 2 into 1, a film by this year's Turner prize-winner, Gillian Wearing, and Misfit, by Sam Taylor-Wood. Wearing's film transposed interviews in which a mother and her two boys talked about each other. This had an element of a cartoon fun to it - but when a schoolboy with the voice of a middle-aged woman said, "He says `I'm a failure', which has hurt me because I think I'm a failure" the sense of unwanted emotional legacies was very striking. Taylor-Wood's film at first seemed rather dull - Kylie Minogue, naked to the waist and miming to an ancient operatic recording - but her static androgyny and the never-satisfied hope that she might turn and show her breasts was retrospectively enlivened by the revelation that the voice belonged to a castrato. In Angel, Mark Wallinger ran film backwards to produce a weird annunciation in an Tube station and in Warren Beatty's Coat, Station House Opera used stop-motion techniques and many bags of flour to create a strange, glacial poetry. Whoever devised the series' title sequence - an inventive set of sight gags involving a man in blue - deserves a pat on the back as well.