Licking the backs of toads to get high.
Based on an urban legend dating as far back as The Seventies, groups of hippies and teenagers were alleged to have been licking specific species of toads which secrete psychoactive compounds through their skin that can cause hallucinations.
While there are toads that do secrete such chemicals, licking it off a toad itself is very dangerous (they are toxins [...] [tvtropes.org]