Hell of a lineup at the final dinner party -- surprising or not? not really, when you take away everyone who existed because of a time loop. But dramatically I think it's hilarious Hannah is still there. Just looking at the show as soap opera, she would have been one of the master queen bitches of the show, who audacity knew no bounds as the season unfolded. [Katharina had her moments as a bully, but we see her fate in the series + enough of her backstory to realize she was in turn abused, so her aggressiveness makes more sense. But we get no context for Hannah and why she did what she did or wanted what she wanted.
Woller never does tell us what happened to his eye. This might have been one of the most subtle yet hilarious running jokes in the series. The last few minutes are the writers jokingly snubbing us a final time.
So really it comes down to feeling like a fever dream. That's not the case in total, as the worlds were actually created, but time travel made them more convoluted and unreal, with reality becoming a sheer hell of sorts. But it's remarkable that the actual story is really centered around what might be a minor character in the series and how that family drama played out -- and how man's desire and pain exceeds his grasp. The inability to grapple with huge pain... the desire to control... the heart wants what it wants, but there are some things that it is not meant to have.
While MARek TAnnhaus is iffy, Sonja as an anagram of Jonas can't really be denied. Of lesser import but of equal interest is how Hanno became Noah.
The two worlds we spend the series aware of: I'm pretty sure they just used the same sets and just inverted the film, as I think some of the character quirks were mirrored rather than appearing the same. Charlotte's eyes, for example, one of her eyes is squintier than the other, but was flipped. I think Claudia's two different colored eyes were flipped. And so on. I'm pretty sure they did this trickery with just flipping the film, and just mocking up the occasional wording that might appear either in the props or via easy CGI.
For the series to work, I felt like Jonas and Martha really had to sell their attraction (something transcending time and space) to each other, two universal spirits in orbit of each other, and Hoffman and Vicari really sold the goods. They took my breath away, and often through an understated performance. I totally bought this.
I thought it was really interesting that Tannhaus needed a replacement Charlotte to anchor him, and there was speculation about what might have happened if he had repeated his initial folly within the looped worlds, splitting them endlessly. dear god...
It was funny how some character traits persisted through worlds. Hannah always wanted Ulrich, at least most of the way through. Ulrich was a habitual cheater; in world #2, he was a cheater on the woman he cheated with. Helge always lost something; attacked as a child, the side of his head was disfigured, while attacked as an adult it was his eye / front of face. Regina always had cancer.
The two world twist seemed really out of the blue at first, then made total sense as the mind moves away from a single-world endless loop into more of a Mobius strip of sorts, where they endlessly loop but cross in the middle to there's two versions of the world that have to repeated, joined at a moment of time (where time briefly stops), thus seeming like two different realities are occurring at once. This is visually perfect as well, because it is the infinity loop itself, even the oroboros represents the single loop. But also... note in actuality that it's only a loop if we are viewing it deterministically; in actuality, the circle exists all at once, just as the infinity loop (which is like two loops) also exists all at once and is really both loops superimposed over each other simultaneously and both already existing. Our brain just finds it easier in a sense to view it as a deterministic loop, going around, alternating back and forth... and yet this is also why we humans get confused as the determinism becomes more convoluted and complex. Again, step back and just see it as two worlds, each feeding into each other, existing simultaneously at all points in time in the loops, so they are completely self-sustaining and fixed... aside from the loophole moment, which I guess is a brief instance where something can "drop out of the loops" and/or is the exit to the minotaur's maze. // Note this also applies to the quantum reality of Claudia sending Jonas into the Original World vs NOT sending him -- basically both the regular time stream and the infinity loop worlds both exist simultaneously for a blip in time, but because there is a reality where Jonas and Martha enter OW to save Tannhaus family, this immediately solidifies that reality and it becomes the outcome, eradicating the choice/reality that contains the Infinite Loop with Adam and Eva's worlds.. The Infinity loop is really fascinating because it only exists for a blip and yet is infinite within itself, all the choices and options existing all at once even if we can try to track it through a deterministic through-line.
Saw a comment about how Mikkel's trick in S1E1 is a shell game that describes the series -- my mind can take that idea and expand it, as the series in a sense is about our getting caught up in all the loops and who is / isn't around or who everyone is, yet both tokens are there at the same and it's all misdirection in terms of the actual problem that needs resolved in order to set things right. You can only solve it by stepping into the world outside the two cups, where the magician is situated.
I might have noted elsewhere this show really reminded me of the film
Donnie Darko in some ways, and by the end even moreso. Even aside from the name.

Donnie might have special powers that Jonas and Martha don't have per se (aside from being unable to be killed except at the preordained times), but they're trapped in loops. Donnie fixes reality by completing the bootstrap loop, but it ends in his death... and yet he finds piece in that while others grieve. Jonas and Martha fix reality in a different way, by negating the discovery of time travel that originally split the world and cursed it into what amounted to an eternal hell, but it's the same level of sacrifice, resulting in the same level of bittersweetness -- all the protagonists find something enduring / some kind of peace, but it's also an ending.
I could go on but be here for days.