Human horn

Human Horn is a slang term for the nose of a human. It is a used as a popular aphrodisiac on alien worlds. Use of Human Horn is often frowned upon in polite society, and its sale and possession is illegal on many worlds. Nevertheless, the burgeoning market for Human Horn has led to the abduction of humans for harvesting of their "horn."

The Lower-Horn
After becoming a victim of a Human Horn harvester, Fry travelled to Omicron Persei 8 to retrieve his nose from its purchaser, Lrrr. After a comment by Bender, it was revealed that alien cultures mistakenly believed that the human nose was actually a reproductive organ. In order to rekindle his attraction for his wife, Ndnd, Lrrr ordered the removal of Fry's "Lower Horn".

Appearances
Since the "human horn" is the nose of a human, it technically appeared in every episode, but this list only includes the use of the term.