For number 2 I wonder if peeps are tagging leggings rather than legwear (which probably shouldn't really be added manually in the first place because it's a group tag)
EDIT: wow, that tag is almost exclusively mistags, it dosn't help that leggings implies legwear eventhough the wiki discribes them as "pants" so even if they were tagged on the right things they'd be implying wrong tags... I think. Might look into it more in the morning.

For number 3 fictional species imply their source series (at least semi-modern fictional species, unicorn doesn't imply whatever the ancient origins of those things are), koopa_troopa implies mario_bros, chao implies sonic_(series), and umm... I'd probably be able to think of non-video game examples if it wasn't 5 a.m.... whatever, why should cheshire_cat be the exception?
EDIT: Oh, namekian that's one! It, uh.. dosn't imply dragon_ball but it probably would if it had more posts.