Alchemy is defined by Merriam-Webster as "a medieval chemical science and speculative philosophy." It in fact predates the medieval period, going back to ancient Egypt. While some aspects are considered a forerunner to modern sciences such as chemistry and medicine, most of the ancient beliefs and practices have long since been refuted. In Europe, alchemy tended to focus on the transmutation of metals (including into gold), while alchemists in Asia sought an elixir of immortality or a universal cure for all diseases.

As early as the 14th century, alchemy was increasingly thought of as a pseudoscience or even a fraud, and later adherents instead chose to apply occult or esoteric interpretations.

References

• Muppet Labs may be where the future is being made today, but in episode 504 of The Muppet Show, they look to the past. Dr. Bunsen Honeydew discusses the failed efforts by alchemists over the centuries to transmute lead into gold (admitting it would be "so snazzy"). His invention instead turns gold into cottage cheese.

• The Mystic urTih in The Dark Crystal is an alchemist and, according to The World of the Dark Crystal, primarily interested in transmutation in general.

• A Bob LaBrea High School student in the Dinosaurs episode "Scent of a Reptile" is carrying a book titled Alchemy (as a joke about how ancient the dinosaurs belief system is, rather than a chemistry or science book).