League of Legends (LoL) Question: Gwen W Question

In the wiki it states that "All projectiles targeted at Gwen by enemy champions outside the mist are destroyed upon attempting to pass through the mist or being inside the mist." And since fizz's R is a stopped projectile you will not get affected by anything.

man the fizz ult is a skill shot

You can't get hit by Fizz ult when he's outside of the W, it would pass through you. If he places it on you when he's in it and then leaves the circle it does nothing to you.

It'd still go off, but you'll likely not take any damage from it.