Rei no Are (例のアレ, lit. “That Thing”) was the miscellaneous category that was added to Niconico on January 13, 2010.¹⁾ Over time, it'd be associated with homoneta, MAD videos, etc. While the categories are now deprecated,²⁾ the tag remains in use to this day.

On January 13, 2010, the staff of Niconico Douga decided to remove the “Fashion” category and add a “Rei no Are” category for certain videos that didn't seem to fit anywhere,³⁾ namely Gachimuchi and Airmoto. The videos had their category changed to “Rei no Are” and this was tag-locked in a way that the uploader couldn't change it, so some users rebelled and started placing Airmoto videos into the “Diary” category.

It started out as a category for strange content that was hard to explain, thus the name, or possible nuances that risk being deleted by management. After two years, the category narrowed down to MAD videos and internet memes. By 2015, the category was dominated by Inmu videos and people generally had no problems categorizing the videos into the “Rei no Are” category.

• Rei no Are on Niconico Encyclopedia
• Rei no Are Dictionary
• Rei no Are on Pixiv Encyclopedia