[GAMEPLAY] Gankplank Double Ultimate Exploited

I've never seen it before but as my team and I push the first mid base turret, GP ults us. Normal.

Then he immediately ults us again and all of us are confused to no end because how???

So after downloading the replay and watching to make sure that maybe it wasn't a visual bug (even though all of us, his twitch included were going "wtf"), I discovered that he knew about it, he flashed his mastery 6 and ulted, then he flashed it again as he ulted a second time in a row. I know of no rune or anything that would allow anyone to ult that rapidly in succession.

Because I'm dumb and for the life of me I'm too lazy to format and edit the replay file to put on YouTube...it's my Miss Fortune Support game 11/26/17 10:20-ish.