Had an issue in my last game where I was playing Neeko and somehow, mid-teamfight, my stats were set to some exceedingly low numbers (420 hp, 12 armor, 0 mr). This persisted after I died and re-spawned.
After reviewing the replay, it looks to me like what happened was I was in disguise, channeling my ult, and then was polymorphed by the enemy Lulu. The bug seems to have kicked in just as my ult completed.
Unfortunately I don't really have anyone who could help me reproduce the bug (since I would need a Lulu to polymorph me at the exact right time), but since it was so massively game-breaking I thought I'd report it anyway.
Replay of Bug occurring: