Rei no Are (例のアレ, lit. “That Thing”) was a 'miscellaneous' category on Niconico that was added on January 13, 2010,¹⁾ and it would become associated with homoneta, MAD videos, etc. The categories were removed in 2019, yet the tag still remains in use to this day.

On January 13, 2010, the Niconico staff removed the 'Fashion' category for a 'Rei no Are' category for videos that didn't seem to 'fit' anywhere,²⁾ specifically Gachimuchi and Airmoto. Some of these videos were forcibly changed to the 'Rei no Are' category and couldn't be changed, which led to a small uproar where some Airmoto videos were categorized under the 'Diary' category in an act of defiance.

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