Darwin is actually the 8th fish owned by the Watersons. So he is really Darwin VIII.
The episode aired in Italy on February 12, which was chosen due to it being Charles Darwin's birthday.
This episode was originally going to be titled "The Roots." This title was later used for another episode.
The shirt with the logo that Richard is wearing is a reference to the American rock band, Nirvana.
This is the first two-part episode in the series.