I believe this is a bug. Annie stun visual.

I wish it was easier to just link a replay. And I'm too lazy to edit a screenshot to omit player names. Basically I was playing a game as Sivir, and I noticed Annie had stun animation (the white swirling lines around her). So I would proceed to spell shield her next ability, only to be stunned by the very next ability. I noticed that her stun animation never left her. At first I thought it was some sort of hack that she just eternally had stun up. Until I looked at her buffs. Her stun charges were going up as normal, and she was indeed only getting stun after 4 spells. But the swirly line stun visual animation never left her, which imo, can be very misleading. I definitely died like 3+ times spell shielding spells that weren't actually going to be stuns, because the animation around her indicated that they were going to stun.

TLDR; Annie stun visual (swirly lines around her) remained on the champion indefinitely, even when she didn't have stun up.

EDIT: I was informed I didn't have to censor names if I wasn't being negative about people. Here is a photo of Annie clearly with the stun animation around her, and me mousing over her pyromancy buff showing x1 stack. This happened midway through the game, so something must have triggered it. But it persisted throughout the entire rest of the game. http://s648.photobucket.com/user/chuvachuva603/media/Annie%20bug_1.png.html