Human horn

"Human horn" is a slang term for the nose of a human. It is a black market product used as a popular aphrodisiac on alien worlds, due to the mistaken belief that the so-called horn is a male human reproductive organ. 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".

Trivia

 * The harvesting process also appears to seal-shut the newly-vacant nasal passages, leading to the appearance of a face with no grotesque holes where the nose once was. When Leela does a quick laser reattachment, it does not reopen these passages, as evidenced when Fry pulls off his nose again to reveal no openings.

Appearances
Since the "human horn" is the nose of a human, it has technically appeared in every episode, but this list only includes the use of the term.
 * (mentioned in text, 7:40)
 * (mentioned in text, 7:40)