Tatl is Link's fairy companion in Majora's Mask. Due to several fans' annoyance with Navi, her counterpart in Ocarina of Time, her "voice" was made a nondescript "tinkling" noise, rather than the "Hey, Listen" associated with Navi.
Tatl and her brother Tael, in the beginning of Majora's Mask, are both aides to the Skull Kid. After a twist of fate, Tatl gets separated from her brother and decides to team up with Link until they can find the Skull Kid, and ultimately, Tael.