I don't know if it was a fluke or I timed something right but I got this to happen.
Hecarim going up top lane, Huge cluster of minions, activated w, enemy champion comes out of the fog, R at them and got so excited about a, more or less, free kill that I activated Ravenous Hydra During Heca's charge, he then proceeded to pause for a second and activate the hydra before he finished his charge.
my build was as follows
Boots of Swiftness - Furor
Spirit - lizard
ability activate order went W, R-Hydra, and then Q
Also I have the Razor Naga mouse with the number pad on the side. Might be a factor in this.
I have recreated twice more in a custom game.
If anyone else can recreate it please post.