In an ARAM game, I was able to use both my q and my w as Annie to stun two or more opponents off one passive proc. For instance, if the Blitz flashed away as I q'd him and I w'd before the cast animation hit him, it stunned both the Blitz (from the q) and Shen (from the w). Not sure if that's supposed to happen but I don't think so.
Do you happen to know if the Blitzcrank got hit by your W as well? If he did, then it's not a bug. What's happening in this case is the W is stunning both of them.
The thing about Annie's Q is it won't consume the stun until it actually lands. Because of this, if you use your Q while you have your stun up, but you use another ability before the Q actually lands, then that ability is the one that will consume the stun, and the Q will simply add a stack towards the next stun.
