The two-minute tale of friendship that develops between saucer-eyed Moz the Monster and his seven-year-old host Joe is set to a cover of The Beatles song Golden Slumbers by Manchester band Elbow for what has become a fixture in the build-up to Christmas.
Moz and Joe strike up a friendship based on a mutual love of late-night Scalextric and piggyback games, but staying awake starts to take its toll on the boy and Moz realises he must allow him some peace and quiet.
Joe finds a clumsily wrapped present of a night light under the tree on Christmas morning, and the ad ends with him hearing the comforting rumblings of his friend when he switches it off that night.
The ad is something of a return to the tearjerkers of past years following last year's comedy bouncing dog Buster the boxer.
Director Michel Gondry, who won an Oscar as a writer of the film Eternal Sunshine Of The Spotless Mind and helmed the 1996 Levi's "Drugstore" commercial as well as music videos for Bjork, the White Stripes and the Rolling Stones, said: "When I told my ex-girlfriend I was doing the next John Lewis Christmas film she said, 'You have big shoes to fill, this John Lewis commercial must make people cry, don't forget'. Last week I showed it to her and she cried. Phew."
However the emotion is tempered by John Lewis unveiling what it describes as the "world's first farting and snoring window" at its Oxford Street flagship store, where visitors will be able to see and hear Moz playing in the rooms in Joe's house.
A recording of actor Sally Phillips reading the Moz The Monster story will be available for download from johnlewis.com, Sky boxes and Google Home, with Google customers able to personalise it by choosing their own sound effects.
Once again there is a charitable link to the campaign. The retailer will make a donation to children's charity Barnardo's from the sale of Moz mugs and cuddly toys.
Craig Inglis, customer director at John Lewis, said: "This year's Christmas campaign brings to life the power of children's imaginations and the joy of great friendships.
"Moz and Joe's story is magical and heart-warming and I'm sure it will be loved by all of our customers, young and old."
The ad is screening on johnlewis.com, the retailer's YouTube channel and in stores from 8am on Friday, and will later appear on terrestrial television from around 9.30pm on Channel 4 and on all Sky's own channels.
The store declined to put a price on the ad, saying only that its budget was similar to previous years, when it spent around £1 million on putting each campaign together and another £6 million on television slots.
The ad has again been the subject of intense speculation about its content, with the store stoking the excitement by releasing short previews on social media under the hashtag UnderTheBed.
An American computer science teacher called John Lewis, who endures year after year of Twitter feedback on the retailer's campaigns despite clarifying that he is "not a retail store", has already posted: "Trust me, no one wants to know what's under my bed. #UnderTheBed."