Actually, Kool-Aid comes in a wide variety of colours not found in nature, but the Kool-Aid Man is a giant pitcher of the red stuff who bursts through walls shouting, "Oh, yeah!" The stuff itself is sold in powder form, either in small paper packets of unsweetened (add your own sugar) or large plastic tubs of sweetened. Add water, and you have a punch-like beverage.
Most notably, the People's Temple, led by Jim Jones, is known to have consumed its lower-cost rip-off, Flavor-Ade (grape, I believe), laced with as I recall cyanide. This was part of their mass suicide. It's worth noting, however, that a lot of people were pretty well forced at gunpoint to take it; they weren't as placid as the metaphor suggests. A fair number apparently didn't believe the stuff was poisoned until after they'd drunk it, too. I read a book that included survivor testimony.
