Thundarr: The Barbarian was directly inspired by comic books, with the likes of R.E. Howard's Conan the Barbarian and Flash Gordon.

Thundarr the Barbarian is set in a future (3994 AD) post-apocalyptic wasteland divided into kingdoms or territories – the majority of which are ruled by wizards – and whose ruins typically feature recognizable geographical features from the United States, starting in New York City and working itself to Los Angeles, Las Vegas, Mount Rushmore, San Francisco or Washington, D.C.

Other episodes with recognizable settings are located in Central America, while one is in London. Another notable feature of this future Earth is that the Moon was broken in two pieces, but the gravity of the pieces drew them back together, orbiting at roughly the same height as the intact Moon once did. The shattered moon and the ruins of the former human civilization were caused by the passage of a runaway planet (more resembling a comet) between the Earth and the Moon in 1994, which, from scenes shown in the opening sequence, caused radical changes in the Earth's climate, geography and tidal effects.

However, by the time period in which the series is set (2,000 years later), the Earth and Moon seem to have settled into a new balance. Earth is reborn in a world of savagery, super-science, and sorcery.

Thundarr's "Super Sun Sword" while visually looking akin to a Star War's "Lightsaber", the method the "Sun Sword" is ignited is more like "StarChaser: The Legend of Orin"'s sword.

In this "way far future world", anything left of "Old Earth" is in ruins, so the main characters mostly "fight evil wherever they find it", while the once familiar land marks are usually just backdrop placings. We the "audience" might know where the "heroes" are, but it is very plain to see that most of the time the "heroes" do not. Even the magic user Ariel can get lost upon occasion, even though she mentions a lot that she is from (and has lived in) "Old Earth" (aka before the Great Cataclysm). Looks quite good for being over 2000 years old.