The Imperium invaders and their equipment are based somewhat in appearance to DC Comics' villains the White Martians but show a tribute to H.G. Wells's classic, War of the Worlds (General Wells, introduced here, is named after Wells). Like the Imperium, Wells's Martians use three-legged war machines equipped with ray devices that easily overwhelm Earth's military, and a "black smoke" that blots out the sun.
Superman is on screen for exactly 7 seconds before he was knocked out. This becomes a reoccurring theme on the series.
The character of Lucas "Snapper" Carr, who appears as a TV news reporter in this opening three-parter, served as an honorary civilian member of the Justice League in the comics. There, he was a "hip" teenager, meant to reflect the emerging youth culture of the Sixties. One of his key characteristics was a tendency to snap his fingers, hence his nickname. A reference to this is made in this episode when he snaps his fingers to get Superman's attention.
J. Allen Carter, one of the astronauts on Mars from the premier episode "Secret Origins" is named after John Carter, Warlord of Mars from several classic science fiction novels by Edgar Rice Burroughs. It could also be viewed as homage to the names Jay Garrick, Alan Scott, & Carter Hall (the "Golden Age" versions of the Flash, Green Lantern & Hawkman, respectively).
Carl Lumbly, who plays J'onn J'onzz, later had a recurring guest-star role as J'onn's father M'yrnn in Supergirl (2015), and Phil LaMarr (Green Lantern) played J'onn's brother Malefic.