Yeah, seriously, calm down on the posting. xP I know we're all excited but we can't be doing this for long or I think we might end up getting in trouble.
Tift is the mousey's name. Maybe he should be a weird new species thing that only exists in the Zelda world. (Looks like a mouse, but using the tail whip idea, maybe he could have a small fuzzy looking ball of quills on his tail. That way it's more than just a tail) As for his/her importance in the story, that squeezing through small holes idea was good. How bout this though, Link ends up getting trap while the baddie ignored Tift, so you play as him/her to go save Link. (This could happen more than once, like on stealthy missions if you get caught, you have to get Link with Tift, then restart. xD It will cause people some trouble in later longer stealth missions. Maybe some annoyance, but that'll teach them to be less rash.)
~desu Saba~