Pokémon - Image #791,949

Not to mention it doesn't even have imposter because it transformed after blastoise mega evolved.

Not to mention it's a b*tch in competitive play:

"That's an interesting Mega Evolution you have there…"
"It would be a shame if someone copied it…"
"Defeated your's…"
"And wreck'd your entire team with it…"

(Which is what happened when I Choice Scarfed my Imposter Ditto and copied my opponent's Mega Kangaskhan, using Power-Up Punch.)