“What if there were a medicine that could heal almost anything? What if they didn’t want you to know about it?” So goes every health grift, preached by everyone from snake oil salesmen to chumbox clickbait to, probably, the U.S. Department of Health and Human Services in the not-too-distant future.

But no, really: What if?

This is the premise of Adult Swim’s Common Side Effects. And if the ingredient at its center sits squarely and obviously within the realm of science fiction, the all too plausible consequences that ripple out from its discovery are what make the animated thriller feel furiously relevant, dryly hilarious and strangely haunting.

The panacea in question is the “blue angel,” a rare Peruvian mushroom with the nigh-supernatural ability to cure anything from dementia to gunshot wounds to, possibly, death itself. It’s the groundbreaking find of Marshall Cuso (Dave King), a genius with the bare chest,...