* AuthorsSavingThrow: In the afterward for ''Zoe's Tale'', Scalzi admits that a major motivation to telling a parallel story was to make Zoe returning with exactly what the Roanokers needed feel like less of a DeusExMachina. It also let him give some closure to the werewolves.
** ''Old Man's War'', as an homage to ''Literature/StarshipTroopers,'' was naturally committed to a CrapsackWorld view of the universe in which humanity's only options were extinction or perpetual warfare against any race capable of occupying Earth-like worlds. (Though even in that book, the StrawCharacter [[JerkassHasAPoint 'has a point']] and the Consu clearly aren't following the CDF's script.) ''The Ghost Brigades'' and ''The Last Colony'' invert this bleak worldview entirely, suggesting that many alien races ''can'' come to long-term peaceable agreements about territory - which leaves the CDF an example of HumansAreTheRealMonsters.
** Many aspects of ''Old Man's War'' can lead to some rather nasty FridgeHorror regarding just how certain aspects of the Colonial Defense Forces work, in particular the use of BrainUploading to extend life by transferring a human's mind into a BlankSlate clone, or the use of enhanced BlankSlate clones sans personality to create what are essentially ChildSoldiers. The sequel, ''Ghost Brigades'' is largely an [[DeConstruction exploration]] of much of this FridgeHorror to show that many characters InUniverse have similar concerns both about the SuperSoldier program and the state of humanity's foreign policy.