A misspelling found by fans in the game's code explains why the computer controlled leaders in the game focus on developing religion over anything else. By spelling the word "yield" as "yeild," a complete group of routines are ignored by the game's programming that are specific to how the computer processes their research strategies.

One of the billboards on the Broadway world wonder shows the profile of a Sectoid, one of the many types of alien from the XCOM series.

Frederick Barbarossa's cape clasp has the Firaxis Games logo engraved into it.