El-Hazard borrows elements from many science fiction stories. Buffs (sci-fi otakus) may have noticed similarities with Princess of Mars by Edgar Rice Burroughs. This novel was director Hayashi's greatest source of inspiration for El-Hazard. Uhra is one character that was "borrowed" from that story. Another influence is the Skylark series by E.E. Doc Smith. A character in the series is rumored to be the inspiration for Jinnai's character.
Peeking up at Lillian's area, another aimless facts™ to note is that the Bugrom did not keep their Japanese names in the English dub (though all of the other characters did). Instead, Pioneer decided to name them after the Marx Brothers.
You may never have guessed it, but Jinnai and Yuu from Marmalade Boy share the same voice actor in Ryoutarou Okiayu. And you thought it impossible that Jinnai and Nanami were siblings.