On Kromagg Outpost 113, humanity never evolved.
On Nouvelle Versailles, North America was colonised by France in the 16th Century.
The scenes in which the sliders are interrogated by the Kromaggs using psychological manipulation were inspired by the Ebonites'
similar interrogation of the Unified Earth soldiers in Nightmare (1963). This is the series' co-creator and this episode's screenwriter Tracy Tormé's favourite episode of The Outer Limits (1963). He later co-wrote its remake Nightmare (1998) with Sam Egan.
On Kromagg Outpost 66, most of the major population centres of Earth were destroyed by the Kromaggs.
The fictitious word "Kromaggs" is based on the factual "Cromagnonman". The Cromagnon are actual early hominids who may have coexisted with the Neanderthals.