Akali W Mark bug.

Akali uses mark on target. Akali starts to jump on marked target. At the mid-air press W. Fog is placed at the initial position of where you started your mark jump from. You are also teleported back to initial position.

Conditions: Mark target is Malzahar with passive active before mark hit. Map is ARAM.

Watched this on my replay with slow motion few times. And its clear.

Edit:

You cannot cast abilities at the midair of mark. But I am pretty sure that I have not cast that smoke there. Also added video. video