The Hitchhiker's Guide to the Galaxy has this to say about the Joopleberry: The joopleberry shrub was a pinky russet plant that grew on the home planet of the Shaltanacs: Broop Kidron Thirteen. It was used in a version of the saying: "the other man's grass is always greener". However, because of its colour, the Shaltanacs used the alternative phrase: "The other Shaltanac's joopleberry shrub is always a more mauvy shade of pinky russet". Broop Kidron Thirteen was known for being "somewhat eccentric botanically speaking."
The Shaltanac race of Broopkidren 13 had a similar phrase, but since their planet is somewhat eccentric, botanically speaking, the best they could manage was, ‘The other Shaltanac's joopleberry shrub is always a more mauvy shade of pinky-russet.’ And so the expression soon fell into disuse, and the Shaltanacs had little option but to become terribly happy and contented with their lot, much to the surprise of everyone else in the Galaxy who had not realized that the best way not to be unhappy is not to have a word for it.”