Sunday night is serial night. Fridays and Saturdays are hopeless (people keep going out, miss episodes and give up) and weekdays are stuffed with immovable news bulletins and soaps. But on the Sabbath night, millions of viewers (like the kids at the long-lost Saturday-morning pictures) are in a mood to be romanced by on-going tales and familiar characters. So what better time to run your serials (same characters, one story) and your heart-warming series (same characters, many stories)?

So, on BBC1 at the moment we can watch that favourite of Tony Blair's, Ivanhoe, and on ITV there is Catherine Cookson's The Wingless Bird (this clumsy title presumably exists to differentiate it from August Strindberg's The Wingless Bird, in which the heroine destroys her husband, castrates her lover and commits suicide). Ivanhoe is a boy's story with a boy's hero. The Wingless Bird is a girl's story with a girl's heroine. Boys' heroes say little and always end up killing their enemy. Girls' heroines, by contrast, say a great deal, and end up marrying theirs.

This post-watershed Ivanhoe begins with a scene from Lawrence of Sherwood, where the half-naked hero is being lashed, TE Lawrence style, by a camp Austrian sadist. Unhappily this is as much sex as we get in episode one. Next we are in a recognisably English fictional forest. Recognisable, because it is absolutely full of roaming characters, explaining bits of the plot to each other. The Normans are riding through with the venal friar, the peasants are out there with their pigs, nasty forest wardens are on the look-out for poachers to hang, and a mysterious pilgrim (a returned Ivanhoe, naturally) is lurking behind trees. So many people in such a small arboreal space, following so many different enthusiasms and occupations, makes the whole thing feel as though it was shot at the Sherwood CenterParc.

Beards are the key to racial identification. The shorter your beard, the more villainous and effete and Norman you are likely to be. At the end of the spectrum, spiteful and catty Prince John has a teeny- weeny triangle of beard half-an-inch below his weak and petulant chin. The Saxons, by contrast, all look like guitarists from ZZ Top. They roll in the straw, eat ferrets on a stick (basted in something unspeakable - the bits of which stick in their copious facial hair), and they speak with Yorkshire accents. All except for the sassy Princess Rowena, who has been to the medieval version of a finishing school, and has an accent like Nicola Horlick. This lass could bring up 10 kids, keep a castle clean, wield a battle-axe and hold down a job in the City, no problems.

The trouble is that Rowena's very competence reminds us just how tedious the hero is. The only thing he's good at is bashing people up. He is inarticulate and humourless (all of which is Sir Walter Scott's fault), while the villain is far more interesting. If Ivanhoe had been written for girls, Rowena would have ended up pulling the bed curtains with Brian de Bois Guilbert - now of course reformed, but still romantically difficult.

In Catherine Cookson land it is 1913, war is approaching and the Suffragettes are on the move. We know this because a clever old lady manages to tell everyone in just one dinner party ("Now women are coming to the fore!" and "Just watch the Kaiser. It'll be war, my boy, war!"). She's right, too!

Our heroine, Aggie, is an old maid of 22, ambitious to sample the finer things in life but stuck in the family sweet-shop, making sugar mice and really running things - though she is unappreciated by her troubled family. This consists of a pregnant, unmarried sister, a father descending into drunkenness because of his loveless union with Aggie's frigid mother, and a would-be brother-in-law from the other side of the tracks. She may not be a beauty, our Aggie, but give her a makeover, bring her to the big house, take her to the ball - and gee whiz! It's every girl's fantasy, made even better by subversive moments, such as when her Higgins-like upper-crust suitor offers to lend her a book. "Madame Bovary!" she exclaims. "But I've read it!" Squelch.

There is also a long-gone decorousness, exemplified by the scene in which she meets the Man Who May Love Her for the third time in the train. A tear comes to her eye. "It's my sister." "Can I help?" "It's too late, the damage is done." "Oh, I see." What does he see? It could be cancer, it could be emigration, but somehow he knows she's up the spout and unmarried. Presumptuous sod. She won't marry him, I hope. I can hardly wait to find out.

There are no such problems of anxious anticipation when watching the phenomenally successful Ballykissangel (BBC1, Sunday). You have seen it all before, many times; in All Creatures Great and Small, in Heartbeat, and in Hamish MacBeth. All set in a small, photogenic rural community; all featuring an invariably male hero, who is also a young authority figure (new policeman, junior vet, doctor, priest, etc). The love interest is always a Rowenan young woman, with whom he negotiates his way through the cast of local entrepreneurs, daft wide- boys, elderly eccentrics who prop up bars and dispense wisdom and regional history in a thick local dialect, and supportive older women.

All Priests Great and Small will feature three or four interlocking plots; at least two - one serious and another comic - must be resolved within the episode, while one or two will become running plot-lines. This week we had the sacked teacher (reinstated by deus ex machina), the beaten wife (rural life has its dark sides too), the wide-boys' madcap scheme for attracting tourists (straight out of Hamish MacBeth) and a running gag about the policeman and his wife trying to have a baby. Terribly predictable, formulaic and pleasant.

Dark Skies (Channel 4, Monday), the new alien-bosh series, is also good fun. The premise is that we're in the America of the Sixties, aliens have invaded the world, and a secret and unaccountable government agency is combating them. And the chief fun is in spotting the extraordinary lifts from movies and other TV series that are incorporated into the show.

We begin with portentous captions from Close Encounters: "60,000ft over Peshawar, Pakistan, May 1, 1960". We then find ourselves in the political world of Washington Behind Closed Doors, with congressional aide John Loengard. But this is mixed with The Invasion of the Bodysnatchers, as aliens take over one human at a time. (They do this by means of creeping snot, with which they cover victims from foot to head. The snot climbs up and enters via the cranial orifices - though only half as much snot would be needed were entry to be made lower down.) Those so occupied suffer nosebleeds, headaches and bouts of mild sarcasm. What is inside them is straight from Alien - a psychotic hermit crab, wriggling about and making strange cat-like growls. Then we pay homage to Forrest Gump by the incorporation of real events and people into the preposterous narrative. And finally the X-Files ingredient of the individual against the state is added: "The truth is down here. Third door on the right."

Rubbish, of course, but before we over-react to all this paranoid mumbo- jumbo we should remember that these fashions disappear. Just a couple of years ago everything was serial killers - now even books on Fred West fail to sell. And though it's true that the Roswell myth is to the credulous folk of the late part of our century what the Protocols of the Elders of Zion were to our credulous great-grandparents, we can reflect that - fortunately - there are no real aliens for us to persecute or stick in camps.

But if it's strange phenomena you're interested in, consider the inexplicable success of Anthea Turner, mega-star. Anthea, who is like an Anne Diamond without O- levels, presented the first Pet Power (ITV, Tuesday), which told tales of heroic canines and colourful guinea pigs. I will leave you with her link, spoken just before the commercial break. "Who said," she asked, " `There were three in our marriage and it got crowded'? Well, there are three in our next story. And one of them has a beak." Wouldn't you prefer the creeping snot?