"Bart: 'Dad, are you licking toads?' Homer: I'm not NOT licking toads." - The Simpsons
The Sonoran Desert Toad, Bufo alvarius, note enlarged paratoid glands
The Sonoran Desert Toad is a large amphibian native to the lower Colorado River area of Arizona's Sonoran Desert. It is large, green, and can be quite aggressive if provoked. It has a special surprise for predators that try to make a meal of a what would at first glance be a feast for many a desert animal.
Look but don't touch, and definitely don't lick this toad.
The Sonoran Desert Toad has been made famous because of its potent toxins. Dog owners report seizures, high fevers, and rapid heart beat in their dogs following unfortunate encounters with this toad.
In fact the poison is so toxic that the Sonoran Desert Toad is responsible for more canine deaths per year than Rattlesnakes. Remember to keep an eye on your dog during summer monsoons so that you can avoid any unpleasant experiences with this amphibian.
Because of its potent toxins the Sonoran Desert Toad has made its way into pop culture. Any references to "licking toads" are often referencing this species, which produces copious amounts of the potent neurotoxin in its enlarged paratoid glands (the fat pockets behind the ear in the first picture). So yes, this desert amphibian has even been referenced on an episode of The Simpsons, though the writers did not identify the Sonoran Desert Toad specifically as the one Homer "did not not lick".
Some anthropologists have suggested that ancient peoples of mesoamerica used a toad as a ritualistic hallucinogen, citing mythological representations of toads. If the peoples of mesoamerica did use toads in ritualistic ways, it was likely this one due to the potent, hallucinogenic nature of its toxin. In the past some suggested that the Cane Toad, found further South, could have been used in this way, but its toxin is more a pure poison than a hallucinogen.
Many media outlets have reported that people have resorted to extracting this toad's toxin and smoking or ingesting it to gain a desired hallucinogenic experience. Given the high toxicity of this toxin and the contracting range of the species this action can be both illegal and stupid.
Interestingly, the toad's toxin is not a banned substance but drug enforcement officials have prosecuted drug offenders by inciting bans on the exportation of this toad(in States where the toad is not native). The Sonoran Desert Toad is protected across some portion of its range, so officials have used the legal protection of this toad to prosecute drug offenders who would use the toxin for a cheap high.
References and Further Reading:
Musgrave, M. E., and Doris M. Cochran. "Bufo alvarius, a poisonous toad."Copeia 173 (1929): 96-99.
Hanson, Joe A., and James L. Vial. "Defensive behavior and effects of toxins in Bufo alvarius." Herpetologica (1956): 141-149.
Weil, Andrew T., and Wade Davis. "Bufo alvarius: a potent hallucinogen of animal origin." Journal of ethnopharmacology 41.1 (1994): 1-8.