If I had Doubling Season in play, then I cast any planeswalker, would my opponent be able to destroy it with Hero's Downfall or exile it with Anguished Unmaking before I am able to activate any of its loyalty abilities?
I know the way priority typically works: you can activate the ability first, but since doubling season is a trigger, I am curious if my opponent could cast an instant while it is on the stack or if the planeswalker would be doubled as it entered, and then my opponent could not respond before I am able to activate it.