Hey, remember when Christmas used to last 12 days? Now it’s so bloated it’s virtually an epoch, lasting twice as long as the year it falls in. The early-warning signs keep changing: not so long ago the start of the holiday season was signified by the release of the Christmas edition of the Radio Times. Now it’s the annual unveiling of the John Lewis ad, which this year features a boy arranging for a trafficked overseas bird to be smuggled into the country inside a small container and presented like a gift-wrapped object to the laddish penguin mate who exists only in his troubled mind. They say psychopathic murderers often start their “careers” by doing ghastly things to animals: hopefully they’ll keep the storyline going year after year, as his illusory brain-penguin commands him to carry out increasingly hideous yuletide ceremonies, until eventually the advert consists of nothing but him appeasing the Penguin King by dancing in the moonlight wearing a necklace of ears and eyeballs, all of it seen through the sights of a police marksman positioned on the roof of a neighbour’s evacuated home.

But this year, the John Lewis ad has been overshadowed by gargantuan supermarket and noted humanitarian anti-war campaigner J Sainsbury PLC, and its tear-jerking period piece in which a perfectly good war is ruined by a tragic outbreak of football.

Shivering in a frosty trench – or “the frozen aisle”, in Sainsbury’s parlance – they pause to sing Silent Night, have a kickaround with their German counterparts, and bond over a chocolate bar. It’s all very poignant, if you mentally delete the bit where a supermarket logo hovers over the killing fields, which you can’t.

Boringly, the advert stops short of showing us the events of the following day, when war was resumed and they reverted to bayoneting one another in the face. Nectar points for each headshot, lads! Kill two Jerries, get one free!

Millions of young men were slaughtered during the first world war – “body-bagged for life”, in Sainsbury’s parlance – and doubtless as they lay dying in foreign fields, gazing down at what remained of their mud-caked, punctured, broken bodies, gasping their final agonised breaths, it would have been a great source of comfort for them to know their noble sacrifice would still be honoured a century later, in an advert for a shop.

Next year they’re doing the Sharpeville Massacre.

Advertising aside, another new Yuletide signifier is “Black Friday”, a shopping tradition that began in the US and is now apparently “a thing” over here, at least according to press releases masquerading as news items. Every year, on the first Friday after Thanksgiving, hordes of deranged shoppers bite, kick and mutilate each other in a bid to get their hands on discounted consumer products. It’s like watching piranhas strip a cow down to its skeleton, but marginally less civilised. I used to think it would take a lot to make civil society break down completely – airborne Ebola, say, or a limited nuclear exchange. But no. In reality, the promise of 15% off a Transformers Stomp & Chomp dinosaur is enough to turn neighbour on neighbour in a bare-knuckle fight to the death. Of course, it’s possible the footage of brawling customers has been faked by online retailers, to encourage us to stay at home and click our way to bankruptcy instead. Wouldn’t be surprised.

My Friend Cayla: several furlongs beyond nightmarish. Photograph: Internet

This year, the top Christmas products include My Friend Cayla, billed as “the world’s first internet-connected doll”, something humankind has been crying out for since the earliest days of the abacus. My Friend Cayla is several furlongs beyond nightmarish. Technology has taken a familiar horror movie staple – the self-aware talking doll that suddenly addresses you by name, even when you haven’t pulled its string – and made it a chilling reality.

Yes, Cayla is no ordinary talking doll. She “knows almost everything”, according to the jingle. That’s because she can Google things with her Bluetooth-enabled, computerised mind. She’s essentially Siri in the form of a plastic child, or, as the website puts it, “the doll you can talk to like a real friend!” – which is true, assuming your conversations with your real friends consist of you issuing basic commands and demanding answers to factual questions.

The promotional material shows children asking Cayla nothing more taxing than “How do I bake a cake?” or “What is the tallest animal?” No one uses her to Google medical symptoms or ask for the latest on Isis, although presumably you could, and the news would be all the more disturbing for being recounted by a cold, expressionless plastic child whose eyes and lips don’t even move. Come to think of it, put like that, I’ve just realised she’s the ideal newsreader.

She’s the ideal spy, too. The moment I saw her, I realised there was a chilling near-future horror script to be written about an internet-enabled talking doll that reports back on everything you and your family get up to, to the government, to retailers, and to random hackers in Belarus. So at least I’ve got a future Black Mirror episode out of it. Fingers crossed I can finish the fictional version before the 3D documentary adaptation is launched in our waking reality.