Light entertainment: Saturday: it will be all light on the night

Yesterday, a new Saturday early evening series started on BBC1. And if that doesn't seem like a big deal, remember how rarely it is that the words "new" and "Saturday early evening series" rub shoulders. Get Your Act Together has moved into The Generation Game's time slot, and The Generation Game, as its name suggests, has survived 28 years and three presenters. The next programme is Noel's House Party, which has been partying- like-it's-1999 ever since 1991 - 1982 if you count Noel Edmonds's Late Late Breakfast Show. Over on ITV there's Blind Date, and its first ever contestants have now got grandchildren.

Could there really be room in the schedules for something new? Actually, no. At teatime on a Saturday, the commissioning editor's mantra is, more than ever, "Meet the new series, same as the old series." Gladiators is simply It's A Knock Out on steroids. Stars In Their Eyes is a Generation Game game. And I'm sure if you scratch the surface of those medals which Davina McCall presents on Don't Try This At Home (ITV), you'll make out the words Jim Fixed It For Me underneath. As for Get Your Act Together ... it's the old New Faces formula. The bossy title follows the lead of Don't Try This At Home and the idea is just a short step from Stars In Their Eyes: a talent competition in which aspiring musicians are groomed for pop stardom by a team of experts. It remains to be seen whether this grooming includes getting them a part in a docusoap.

Not that I object to how similar these shows are. They have a precise job to do. They have to attract us when we're getting the kids together for dinner, getting changed to go out or getting drunk. Destined to be viewed on the TV in the corner of the kitchen, they have to be something which the whole family can half-watch. We should be able to follow them even if we missed the last episode - or even three-quarters of this one - so it's best if each programme is a chain of distinct items. If you ask anyone in the pub on Saturday night if they saw Blind Date, the response is never "yes", but: "I saw the bit where they went to Mauritius." It's the only way. A bite-size chunk of Blind Date can be a tasty indulgence while you're waiting for your other half to find the car keys, but the show is so insanely repetitive, with its interchangeable guests and tabloid double entendres, that you'd be ill if you sat in front of it from start to finish.

Once you've established the format of your Saturday teatime show, you need to work out the content. You have to interest people of all ages and no attention span. In short, you need ritual humiliation. This usually comes in the form of a challenge: abseiling, karaoke or, on Gladiators, being rugby-tackled by a man in a leotard. Last week Davina McCall summed up her show, and all Saturday teatime shows, as "real people doing the most extraordinary things", and "real people" are essential, too: not real as opposed to holograms, but real as in non-famous. The cameras are trained for much of the time on the studio audience and on the civilian volunteers, so we feel as if we're part of the programme, and that our evening's socialising has already begun. Anything named House Party has a head start.

Don't Try This At Home, on the other hand, has problems from its title onwards. Every two-minutes McCall begs us not to have a go at what we see on screen - just in case we're tempted to tightropewalk between two jumbo jets with a mouthful of cockroaches as soon as the programme's over. I know she has a responsibility to say this, but the incessant reminders of the gap between on-TV and off-TV are not what we want to chew over with our Saturday evening fish fingers.

Challenges aside, the way to humiliate real people is to use sub-Candid Camera practical jokes. Or, in a word, gunk. Comic fads may come and go, but the British public has yet to find anything more amusing than the sudden meeting of human being and 40 gallons of fluorescent green fluid.

And this brings us to another truth: Saturday teatime TV is a direct descendant of the British variety show. Only in this slot will you hear Leo Sayer singing while a bare-footed man climbs a staircase made of scimitars, and a woman is "squashed" by a hollow polystyrene block with 10 TONS painted on the side. It's rather comforting in an age of satellites and set-top boxes - in my young day, the box was the set - to know that programmes as anachronistic as Noel's House Party's stately home are so popular.

The Generation-After-Generation Game has moved with the times least of all. If anything, it's moved backwards - and I'm not referring just to its unshakeable faith in the pleasure of watching people icing cakes and blowing up balloons. Last week, on The Best of the Generation Game 1998, Jim Davidson parodied Rod Stewart singing "Sailing", and then did "Sorry Seems To Be The Hardest Word" as Elton John. Both of these impressions were a couple of years out-of-date on The Best of the Generation Game 1978.

The show's timewarped sensibilities can be less innocuous, too. Once, the programme had a gay presenter. On today's Generation Game, if a man is any good in a flower-arranging contest, Davidson will - ho ho! - pull a disgusted face. He doesn't approve of homosexual relationships. He believes in the institution of marriage, which is why he's tried it so many times.

The downside of having so many reassuringly long-running shows is that in a certain light they look tired and tatty. The latest games on Gladiators favour gimmicks over excitement.Blind Date's attitude to class is pre- war: any male contestant from Sussex has to have a tank top, Hugh Grant hair and public school vowels for Cilla to imitate badly - never mind that he won't have half as much in the bank as she does. And Noel Edmonds's Gotchas - his celebrity pranks - are toothless, mainly because the victims are never inveigled to do anything embarrassing; they merely observe passively as some havoc is staged around them. What with Edmonds being conned into denouncing a fictional drug called Cake on Brasseye, and Chris Evans revealing on TFI Friday how he rumbled and sabotaged a Gotcha that was planned for him, it looks as if the House Party might be over.

There has got be room for a Saturday teatime show that's a little more contemporary: something that gives the old genre some irony and edge - and which has no sign of Noel or Jim. It seems, then, that I've just written long puff for Families At War, the Reeves & Mortimer vehicle that's due on our screens in the spring. If last year's pilot is anything to go by, it's subversive and funny, but it's also got real people, challenges and variety turns. All it needs is gunk.