In The Universe Next Door, the President of Unistat is Furbish Lousewart V; in that universe, a terrorist organization known as Purity of Essence (named after General Ripper's obsession in the film Dr. Strangelove) threatens to detonate nuclear devices in major cities all over Unistat.

The Schrödinger's Cat Trilogy is a trilogy of novels by American writer Robert Anton Wilson consisting of The Universe Next Door, The Trick Top Hat, and The Homing Pigeons, each illustrating a different interpretation of quantum physics. Wilson is also co-author of The Illuminatus! Trilogy, and Schrödinger's Cat is a sequel of sorts, re-using several of the same characters and carrying on many of the themes of the earlier work.