Urectum

Urectum (formerly, Uranus) is a gas giant in the solar system. The planet's former name, Uranus, was often of the cause of much laughter in the immature English speaking world, where its name could be interpreted as "your anus". However, by 2620, scientists finally got tired of that "stupid joke", so they renamed Uranus to Urectum.

Production
The planet of Urectum has never actually been visited during the course of the series, and after its mention in "A Big Piece of Garbage", it has never been mentioned again, as it cannot be used as a joke, due to its renaming. It did, however, briefly appear in "In-A-Gadda-Da-Leela", in a hologram of the solar system.