"Fortune Fairy", known as "Fortune Telling Witch" (占い魔女Uranai Majo) in the Japanese version, is an anime-only archetype consisting of six monsters, each named and colored according to their own Attribute. The card text on each "Fortune Fairy" tells the fortune of the person who draws it, along with a listing of a lucky number, color and item. The lowest Level Fortune Fairy, Hikari, is the best prediction ("Super Happy") the predictions getting less optimistic as they go up in Level, the Level 6 Chee being "Absolutely Awful". (Indeed, in story, Chee is the card Carly draws right before her duel with Sayer, which ends in her death and transformation to a Dark Signer.)
In the first episode that they were used in a Duel, it appears that their play style focuses on summoning as many as possible and as fast as possible, using cards such as "Luck Loan" and "Unacceptable Result", then using "Miracle Stone" to increase their ATK.
All of these cards have a fortune written on them, with lucky number, color etc. The lucky color and number correspond to that monsters' Attribute and Level. The fortune may be based on the luck of you having it in your hand, e.g. it would be unlucky to have a level 6 Normal Monster with 0 ATK and DEF.