A source who claimed to have knowledge about the retailer’s plans this year told OK! magazine that this year’s ad would feature a "big, cuddly monster".
It was then described as a cross between a teddy bear and the Gruffalo, the eponymous character from the children’s book by Julia Donaldson.
Filming for the ad finished two months ago and the film’s final edit is getting "a lot of post-production to get the special effects right", the source added.
The ad, which is due for release in early November, will be directed by Oscar-winning director Michel Gondry, Campaign revealed last week.
John Lewis said it "does not comment on speculation", while Adam & Eve/DDB declined to comment.