Seven-year-old Joe can not sleep because Moz keeps him awake at night, wanting to play.
The pair strike up a friendship based on a mutual love of late-night Scalextric and piggyback games.
The ad is meant to be a return to the tear-jerkers of years gone by - in contrast to last year's bouncing dog Buster the Boxer. The advert was directed by Oscar-winning screenwriter Michel Gondry, the director behind Eternal Sunshine of the Spotless Mind and uses an Elbow cover of the classic Beatles song "Golden Slumbers" as its theme song.
Gondry 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".
Moz the Monster merchandise will be available to purchase on the John Lewis website and in selected stores from the day of launch.
Once again there is a charitable link to the campaign.
John Lewis has chosen Barnardo's as its charity partner and will make a donation to the charity from the sale of Moz cuddly toys and mugs.
'John Lewis is never knowingly undersold and we pride ourselves on knowingly underselling, so the creation of this discount ad both resonates with our customers and reflects the monster discounts we have on offer in partnership with John Lewis, ' said MyVoucherCodes managing director Chris Reilly.
The advert will first be shown on TV this evening at around 9.30pm on Channel 4 and at approximately the same time it will also be broadcast on all Sky's own channels. And if you want to check out even more John Lewis ads, you'll find plenty of them on YouTube.