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Yukkuri Shiteitte ne! (ゆっくりしていってね!) translates literally as “Do it slowly!” but it is more commonly known as “Take it easy!” 
This meme revolves around giant heads with ridiculous facial expressions resembling Touhou characters. Its origins come from 2channel, where an Anon attempted a Shift_JIS art of Touhou’s main characters Reimu Hakurei and Marisa Kirisame. However, the result was considered a hideously epic fail.
Another 2channer thought it was hilarious and drew the iconic original picture:
Here’s a more traditonal version of how Reimu and Marisa appear.
But their fat-headed appearance in the 2channel Yukkuri “re-draw” caught on, becoming an epic meme in Japan.
Yukkuri’s popularity soon spread to 4chan’s /jp/ board, appealing to a wider anime audience. They appear in fanart, doujins, and plushies. Many artists describe detailed Yukkuri behavior, anatomical structure and ecosystem, although since they are purely a fan creation, any rules concerning the creation of a Yukkuri are subject to popular opinion.
Although Yukkuris started with a large Touhou base, recently it has expanded beyond Touhou; anything with a face can be turned into a Yukkuri.
Miku Hatsune – “Yukkuri Shiteitte Ne!”
Yukkuris Take Over the World
Take it Easy! Yukkuri shiteitte ne! (Remix)