Also known as: よつば, 小岩井よつば
The main character from the Yotsubato!. A tiny five-year old girl with a distinctive Green Hair tied into Quad Tails, resemble a four-leaf clover, fitting with her name. Also, apparently not a Japanese.
4chan uses her as a mascot/on their 404 pages and hold her in high enough regard that asking for porn of her gets angry reactions and most often even bans.