"You've Heard of the Elf on the Shelf" is an internet meme.
Description[]
"You've Heard of the Elf on the Shelf" refers to a series of image macro in which the phrasal template "You've heard of Elf on the Shelf, now get ready for" captions an image of two things that rhyme with each other. The image serves as a punchline for the caption.
History[]
Origin[]

fuckin-rockets' post.
On December 3rd, 2016, Tumblr user fuckin-rockets posted a variation with the phrase "You've heard of Elf on the Shelf." Under that caption, they posted a picture of an Ash Ketchum action figure in a garbage can (the implied rhyme being "Ash in the trash"). The post (shown below) received more than 53,000 notes within 10 months.
Precursor[]
"You've Heard of Bigfoot, Now Get Ready for Smallhand" is a word play joke about an unknown rival to the cryptid ape creature Bigfoot. After circulating on Tumblr in July 2015, the joke inspired many variations on the microblogging site using the phrasal template "You've heard of X, now get ready for Y," typically contrasting two diametrically opposed terms.

A tumblr post of "You've Heard of Bigfoot, Now Get Ready for Smallhand" by user fuck-bon.
Spread[]
On September 14th, 2017, Redditors /r/me_irl subreddit began posting "Elf on the Shelf" variants en masse. That day,PM_ME_YOUR_CHEETOS posted an image with the caption "You've heard of Elf on the Shelf, now get ready for" and an image of Shrek on a backyard deck in the The post received more than 19,000 points (19% upvoted) and 200 comments. Redditor pebblesom posted the character Waluigi on a squeegee, garnering more than 20,000 points (93% upvoted) and 280 comments. Additionally, Redditor Havokmin posted a picture of Link from The Legend of Zelda on a sink, receiving more than 5,000 points (95% points) and 85 comments.
On September 17th, Twitter user @nsarmored frog posted a picture of a plush Pokémon Eevee on a TV. The post (shown below) received more than 27,000 retweets and 58,000 likes in two days.
On September 18, 2017 Twitter published a moments page regarding the recent popularity of the elf on the shelf images. Several media outlets covered the popularity of the meme, including TIME, New York Magazine, BuzzFeed, Polygon and more.