Wild Mongrel

What graveyard decks needed in the early days was a creature whose discard outlet was free, repeatable, and bolted to a body that could actually close a game. Threshold and madness archetypes built around it for exactly that reason: every card pitched to the +1/+1 ability filled the bin toward threshold or set off a madness cost, and the creature growing itself was incidental upside rather than the point. The color-change clause looks like a footnote and mostly is, but it sidesteps a color-specific removal spell or slips past a protection ability often enough to matter in a pinch. What makes the card sing is that the discard is undirected: you choose what to feed it, so the same activation that turns a 2/2 into a lethal threat is also how you drop a flashback card or a madness spell exactly where you want it. That double duty is why it became the engine piece every green-based graveyard deck started from for years, and why it stood as a benchmark for how much a two-drop should be allowed to do for free. Plenty of later beaters got better stats; few matched the way this one rewarded you for emptying your hand instead of punishing you for it.