Illaoi W bug.

If Illaoi only has lets say, 30 Mana. That's enough for one Q right? But since Q buffers and the mana cost doesn't immediately gets taken until after the tentacle hits, she can activate W mid cast before Q takes the mana cost and get both spells for the cost of one. This also works with E W if you spam your W fast enough. I want to say it's more of a bug with W than her other spells because you can't do the mana cost for Q E or her ult in any spells just Q W or E W.