The comic brilliantly contrasts delicious lickable items with polonium-210, which is basically death on a stick. Polonium-210 is an alpha-emitting radioactive isotope that's roughly 250,000 times more toxic than hydrogen cyanide. One microgram is enough to kill you painfully. The punchline about "Andrea stopping nuclear war by licking a warhead" is darkly hilarious because it's scientifically preposterous. First, nuclear warheads don't typically contain polonium, and second, anyone getting close enough to lick weapons-grade material would be dead before they could become a folk hero. This is exactly why we keep telling undergrads to stop tasting chemicals in the lab. There's always that one student who thinks the "no eating in the lab" rule is just a suggestion...