This was a pretty solid episode with some very good jokes (the thing about creating a warp field with one nacelle was fantastic, for example), but I left feeling underwhelmed because of the bizare "the first officer is two LTJGs" thing. Lower Decks has had a shockingly strong track record of not doing things that strike me as immediately stupid, but this is really silly. "Ransom must be pulling another twisted prank, because he's not this bad at his job" level silly. I think it's still better than promoting Tilly to XO, but that's a bar I had hoped this show would remain well clear of and a close shave is disappointing.

I think I understand why they did this: there's no obvious non-specialist XO candidate of an appropriate rank in the main cast (arguably Shax, but he's "only" a LT and does not seem ready for the job), and they didn't want to just trot out a handwave and say they'll be picking up the XO at the next starbase or something. I'd also theorize that they had planned to have two more seasons in which to work Mariner and Boimler into positions where they might actually make sense for an XO billet. But they aren't there yet, and they both know it.

Also, gosh would that alternate universe explorer thing have been useful in DISCO S3. And probably Prodigy too. It's also a dangerous can of worms to open for future stories, because having reliable access to random slightly different universes, apparently at different points in their timelines, is incredibly useful for both anticipating and solving problems in the "prime" universe. There's also cool stuff they can do with it and I'm sure they will, so I'm trying to keep an open mind.

Finally, props to them for coming up with a more plausible reason for our heroes to literally save the universe: because someone connected to them got unwittingly thrown into a position of enormous influence, and deliberately picked them. It's Zeus and company antagonizing Hercules, not Michael Burnham being central to solving five (?) entirely unrelated but galactically significant disasters, apparently by pure chance.