The premise is such stuff as comedy sketches are made on: Starships are huge, and staffed by hundreds of officers and crew members, so why does every Trek story need to revolve around the bridge, and the same 7 or so characters? Why not focus instead on the grunts doing the tedious, everyday work?
Enter: the U.S.S. Cerritos, a California-class Federation starship tasked with "Second Contact" missions, which may not be as flashy and high-profile as the "First Contact" missions marking humanity's initial encounters with alien races. No, the Cerritos' remit is, according to by-the-book striver Ensign Boimler (voiced by Jack Quaid), all about following up, which is "still pretty important—we get the paperwork signed, make sure we're spelling the name of the planet right, get to know all the good places to eat."
(Normals, you can skip this paragraph. Nerds, keep reading, here's what you want to know: Lower Decks takes place in the waning days of the TNG era—2380, to be specific, just after the events of Star Trek: Nemesis. And no, you haven't heard of California-class starships before; they were created for the series. Also, the official shorthand designation for the series we're encouraged to adopt is ST:LDS, which makes it sound like a show about Space-Mormons on a five-year mission to seek out planet Kolub, but whatever.)
Creator/showrunner Mike McMahan made his bones on the animated series Drawn Together and Rick and Morty—shows whose darker, more cutting humorous sensibilities would seem to clash with Trek's traditional commitment to ennobling, optimistic uplift. But that disconnect turns out to work for the new series, in most respects. For the nerds, in-jokes and easter eggs abound, testifying to the creators' fondness for the source material, while viewers who don't know a nacelle from a Jeffries Tube will likely appreciate the show's sheer joke-density—and the fact that, as an animated series, it comes outfitted with an unlimited special effects budget.
That's important, because despite its bright, broad, cartoony look, the planets of Lower Decks can appear legitimately otherworldly, instead of all looking like the Vasquez Rocks outside of Santa Clarita, California. Alien races can look alien—obviating previous series' need to, as one wag (me) once put it, "Grab a dayplayer, slap a hunk of spirit gum between their eyebrows, paint 'em Prussian blue and shove 'em in front of the camera".
The overtly comic nature of the series combines with its animated status to drive its tone—and its plots—to extremes of slapstick violence that previous, staid-by-comparison Trek series would never condone nor tolerate. As a result, the U.S.S. Cerritos seems like one of the most hazardous workplaces in the history of Starfleet. (A character gets sliced to the bone by a Klingon bat'leth two minutes into the pilot, just for starters.)
McMahan and his fellow writers seem to recognize this tendency for broadness, and have made clear efforts to keep the show's conflicts grounded in its characters. Tawny Newsome voices Ensign Beckett Mariner, whose reflexively rebellious, obnoxious demeanor belies her considerable competence and diplomatic skills. Quaid's querulous take on Ensign Boimler presents him as a rank-obsessed rule-follower whose interactions with Mariner allow him to begin to shed his considerable inhibitions. Audience-surrogate Ensign Tendi, voiced by Noel Wells, is an eager, just-arrived science officer who's perpetually enthralled by even the most boring/disgusting tasks, and Eugene Cordero voices Ensign Rutherford, an engineer recently outfitted with Vulcan-designed cybernetic enhancements that seek to tamp down his emotional response. (A Trek character who's struggling with the battle between human emotion and logic: Take a drink!)
The show's at its strongest when it sticks most closely to its premise: background Trek characters going about their days, intersecting with the glamorous bridge crew only glancingly, if at all. But over the course of the first four episodes made available to press, our four Ensigns keep encountering the ship's steely captain (voiced by Dawnn Lewis) a ridiculously square-jawed first officer (voiced by Jerry O'Connell) more and more frequently, enmeshing themselves in command decisions.
There's also, at least in the early going, a tendency for the in-jokes to tread ground that many stylish Trek and Trek-adjacent black booties have trod repeatedly by now—the holodeck has prurient possibilities! etc. etc.—which is something the show's going to want to keep an eye on, if the idea is to boldly joke where no one has joked before.
If nothing else, though, Star Trek: Lower Decks, by staking its claim as the officially licensed Star Trek Comedy Series, will likely throw The Orville, with its untenable mix of glib goofs and maudlin drama, into a profound existential crisis.
In interviews, showrunner McMahan calls ST:LDS the "first Trek comedy series," implying that others may follow. The mind races. Then reels. Then boggles. Wacky sexy hijinks on Risa! A fish-out-of-water story featuring a Xindi-Aquatic on a Class H planet! Captain Janeway's hyper-evolved space-lizard offspring being forced to move back in with her!