Since 'Zod' aired, I've been thinking about the way in which Zod's possession of Lex foreshadows future canon Lex, as Superman's opponent. Rewatching the double episode arc, this became even more apparent to me. We're encouraged to think about the parallels on a number of occasions.
Jor-El and Zod
We learn that Jor-El and Zod had a history together, and that while they became enemies, Zod retained a fascination/obsession with Jor-El, which extends to his son: 'You have your father's eyes.' In the struggle between old friends on Krypton, the future of that planet was at stake. Yet, Jor-El did not succeed in killing Zod once and for all. When Jor-El tells Clark he must kill Zod's vessel, he puts special emphasis on the words 'no matter who it may be'. The implication is that Jor-El may know that Clark is facing killing his Zod equivalent: Lex. What the audience knows is that he will face this again in the future, with his own world at stake, repeating history.
The scene in 'Vessel' between Clark and Lionel is also interesting, since Lionel is affected to some extent at least by his connection to Jor-El. Lionel says that the true test of a hero is knowing 'when the greater good will be served by an evil act'. Jor-El had referred to the Vessel as a 'sacrifice', and the challenge that is set up is for Clark to sacrifice his old friend for the sake of the world.
Before the portal for Zod is opened, Lex is prepared for him. During this period, Lex has super-strength and other Kryptonian powers, but in other ways he appears to remain 'himself'. It's as if he's been given a fast ride to the future--he has the power he covets and he consequently feels able to speak his true feelings to Clark, projecting his feelings onto Clark in the bitterest of terms. It's personal.
Once Zod takes possession of him, Lex appears to be completely subsumed. However, the parallel continues: this fight is personal for Zod--this is his final revenge on Jor-El. Zod needs a mate--he accepts Lex's choice of Lana, but reduces her to an object, a broodmare, and she's crucified by male desire in the horrible hand-penetration scene. This is the extreme end of the customary objectification of Lana within the Smallville universe. And Lex is complicit in that. Is this a hint than as he darkens, Lana will become more and more objectified for him? Merely a tool for procreation? I'm inclined to think so given the way parallelism has played out in SV before now.
Two people view Clark as near-identical to his father, though they have different personal images of Jor-El. Rayah adored Jor-El, and sees in Clark his most heroic aspects: she's blind to Clark's faults. Zod, however, sees Clark as 'an idealistic fool like your father': his reading of Jor-El is negatively skewed, and is his undoing. But Rayah's trust in Jor-El/Clark is just as damning, for she also dies. And the truth seems to be somewhere in between--Clark (and possibly Jor-El once too) has both positive and negative attributes. He may be idealistic and brave at times, but he also makes mistakes.
In the final conflict between Zod and Clark, we also get a glimpse of future canon Superman opposing Lex Luthor. Zod offers Clark a partnership, just as Alexander once offered him one. When this is rejected, Zod seeks to conquer Clark, yet it is their closeness that is his undoing. I feel this strongly foreshadows a future canon Lex who will try to capture, enslave and otherwise restrict Superman, but who's undoing will be his emotional obsession with Clark.
Coming out of the Vessel/Zod arc, both Clark and Lex experience, or at least appear to experience, guilt about the destruction wreaked on Metropolis. Clark works round the clock to rebuild the town physically and Lex pours money into it. But to what degree do either of them really need to feel guilt? Opinions on this will differ because of character sympathies. My personal view is that it's healthy for Clark to a certain extent in this instance because he never properly faced the degree to which he was responsible for the events in Season 5. However, I'm certainly not advocating that he wallow in guilt. But healthy responsibility-taking could move him forward as a character. Lex is more of a puzzle--he claims not to remember anything of what happened, in which case, how can he be held responsible? His actions seem more concerned with remedying his image in the eyes of others than true deeply felt guilt. And this is an indication that he's already quite far on the path to becoming capable of the type of duplicitous history-rewriting that Zod tried on Clark through Fine in Season 5.
I'd be very interested to hear what others think: to what degree did you feel the Zod arc prefigured future canon?