Gitaxian Anatomist
Creature — Phyrexian Wizard
An inconsistency in a routine vivisection sparked a revelation about the inner workings of the Orthodoxy's centurions.
Rulings (6)
You don't have to choose every permanent or player that has a counter, only the ones you want to add another counter to. Since "any number" includes zero, you don't have to choose any permanents at all, and you don't have to choose any players at all.
An ability that triggers "Whenever you proliferate" triggers even if you chose no permanents or players while doing so.
Players can respond to a spell or ability whose effect includes proliferating. Once that spell or ability starts to resolve, however, and its controller chooses which permanents and players will get new counters, it's too late for anyone to respond.
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