@Diamona totoro wasn't all
that cute tho, he played more into the "humorously absurd-looking" niche. The ghost-bunnies (furbies) stalking totoro was cuter, but still not winners.
Didn't know of shaman kings kororo, but google images suggest that the tree-girl still wins.
interestingly enough I can't remember other characters using leaves as umbrellas, despite knowing I have seen it quite a lot. Like, I know there were talking animals huddling shivering under large-leaved plants in children shows, but can't remember where or which ones they were :/