The Unbeatable Squirrel Girl

Squirrel tribal has been a running joke in Magic's design history, the tribe Wizards keeps returning to precisely because it is absurd: Squirrel Nest, Chatter of the Squirrel, the whole Deep Forest Hermit lineage. What separates this build from those earlier gags is that it does the two things a token payoff has to do at once, in the same card. The enter-or-attack trigger seeds the board on a curve, so the 4/4 is never a standalone beater sitting on an empty table; it is always adding to a count. The activated ability then turns that count into geometric growth, exactly doubling your Squirrel population each time you pay the (the creature itself is a Squirrel, so it feeds its own math). That resolves the classic token-deck bootstrap problem: generators are worthless with nothing to multiply and multipliers are worthless with nothing to make, so most decks need both halves in different slots. Here the seed and the exponent share a mana value and a card. The only brake is the flat outlay, a rate limiter rather than a tax: each activation still doubles, but you can fire it only as fast as green mana accrues, so the ceiling is set by your lands. And because the doubling carries no timing restriction, it can happen at instant speed, ambushing a combat step or padding the count at end of turn. That the whole apparatus is wrapped around a Marvel character is the surface joke; underneath, it is one of the cleaner one-card token engines the tribe has been given.