Threadhopping with this character?: Sure!! Just let me know via AIM, or in an OOC note on a thread or something.
Backtagging with this character?: Of course! I'll probably be doing the same.
Hugging this character?: Unless you're his brothers, April, or a friend, he most likely won't allow it.
Giving this character a kiss?: See hugging, and expect him to be flustered a little if you do.
Something more intimate?: Uh, eh, sure? Though it won't be easy to get him into bed. Not to mention he's got little experience in it. Plus he's not sure why anybody would want to be intimate with a giant turtle in the first place.
Relationships?: Sure! If you can some how manage to get him to trust the char that much. It wouldn't be easy, though.
Punching this character (provided they can fight back): Sure, just expect him to punch back unless it's just a friendly jab.
Injury?: Definitely! Just anything too bad like loosing a limb, or getting the crap beat out of him(like in Shredder strikes back) or something, please get my permission first.
Death?: If there's a good enough reason, sure. Would just have to run it by me first.
Is there anything you do not want mentioned near this character?: Not really? Feel free to mention whatever around him.
Is there anything you need us to know about interacting with this character?: Leo does not trust easily. He'll most likely be wary and suspicious of anybody until they've proven they can be trusted. You loose that trust, it'll be even harder to get it back.
Anything else, please mention here: He has a close bond with his brothers. If you attack, hurt, injure, maim, or even kill one of them, expect retaliation, and watch your back.