Wow, I never really thought about it. It was interesting Tatl had a brother (Tael) and was 'on the other side' (meaning originally hanging out with the bad guy, the Skull Kid) first (she didn't want to get left behind with Link & didn't like Link at first, so watching the complete turn around was cool); and their whole conversation before entering the moon (Tatl and Tael's that is) was pretty interesting for a fairy companion role (Tatle doesn't want to go with Link, so Tael offers to go, making Tatl change her mind). Navi's story for Majora's Mask always interested me though (Link leaves Hyrule to go find her); that motivation etc. was interesting at the time to me but perhaps not as interesting as Tatl's place in MM. I alwasy wondered what happened to Navi, so the mystery involved is also interesting, but since you can't base how you feel about a character based on loose ends, I pick Tatl.