In-Game Bug
Watch Leadcow's League of Legends video: Such BS - Plays.tv
Happend to me alot of times, chogath´s W is hitting you when you use quick spells to dodge it just as it is about to cast. These spells can be, flash , ezreal E, Jarvan Q+E combo and so on. If you flash just before Chogath´s W is about to be cast, sometimes it hits you any way. Sorry for poor quality on clip.