1 is a one that lives in Number Island. He met up with Link in Link's Great Adventure. He was hated by everybody, and then saw Link. He then realized that he could become popular by killing somebody. Link battled 1 in a climatic battle of epic proportions.
He currently lives with ! in Keyboard Village. Despite being worse than 2, he's a lot better than 0 but is still a loser. He is also a member of the 1234567890. He was also jealous of all the other numbers because his IQ was 1 and everyone else had a higher IQ than him. He is angry at 99999999999999999 and Pi.
He owns two pet swords, and named them Spike, and Killer - Typical pet names. He wields them with deadly skill, but cannot actually use them, because he does not know how. So, he just stabs himself a lot by accident. He has since developed an immunity to swords, and an immunity to intelligence.