* CanonSue: Seaton is this -- his interests, abilities and values are all either those of Smith himself greatly exaggerated, or ideals Smith held. (Indeed, all four of the main "good" Earth-human characters are Sued versions of real people -- Dorothy Vaneman of Smith's wife, and the Cranes of his friends Dr Carl Garby and Lee Garby, Carl's wife who helped Smith with the "romantic" aspects of the first book.)
* DesignatedHero: The Kondalians have practically no traits that would be considered sympathetic by modern readers. They have no concept of democracy, race-based slavery is unquestioned, [[DoesThisRemindYouOfAnything they've been at war for 6000 years over ideology]], are {{Social Darwinist}}s who believe themselves a SuperiorSpecies, and admit to having no concept of mercy. All in all, they are no better than the Mardonalians; the only reason they are considered good is because [[ProtagonistCenteredMorality they were nice to the heroes]].
** Unlike the Mardonalians, and the villains generally in the series, the Kondalians are not [[AbsoluteXenophobe Absolute Xenophobes]], but willing to co-operate peacefully with other planets. That said, they ''are'' typically portrayed as a species of ProudWarriorRaceGuys, with a strong whiff of [[JohnCarterOfMars Barsoom]]. They're ''very flawed'' good guys, and they do occasionally get called out on their warmongering by the human protagonists.
* HarsherInHindsight: TheFederation's war against the Fenachrone. The latter are a bunch of [[ScaryDogmaticAliens malignantly expansionist]] RubberForeheadAliens planning to expand from their own single planet; Seaton and company object to their plans. So far, so good. Their reaction, however, is first to threaten and bully the Fenachrone with their own overwhelming might until they declare war on them in desperation, then -- When as defenders, they hold the moral high ground -- [[EarthShatteringKaboom nuke their planet]] and launch a near-successful attempt to [[FinalSolution exterminate the refugees completely]]. While it's clear the Fenachrone ''are'' aggressive militarists and potentially genocidal themselves, they also aren't really a threat to the vastly superior technology and numbers of the good guys at this point, and indeed have to display a fair amount of VillainousValor merely in order to survive the attempted genocide. Besides the questions of DisproportionateRetribution and general ValuesDissonance, to modern audiences the whole affair also reads a lot like the [[EagleLand Roosevelt administration's]] historical warmongering and bullying of ImperialJapan, which ultimately lead to Pearl Harbor, the Pacific War and Hiroshima.
* HilariousInHindsight: Nowadays, there is a real restaurant chain called Perkins. Considering how the character [[TheBrute was portrayed in the book]], it is potentially FridgeHorror.
* MagnificentBastard: [=DuQuesne=].
* OlderThanTheyThink: A "dark star", essentially a black hole, and mushroom clouds produced by the atomic/total conversion of explosive shells. Both in ''The Skylark of Space'', published in '''1928'''.
** Early drafts are said to go all the way back to '''1916'''. That is ''sixty years before Star Wars.''