Warning: SPOILERS for Star Trek: Lower Decks Season 2, Episode 1 - "Strange Energies".
In Captain Will Riker's (Jonathan Frakes) USS Titan.
Star Trek: Lower Decks is set in the 24th century in the same era as Roddenberry's rule, TNG was still able to create some of the most legendary science fiction television ever made. However, many TNG writers quit over the years because of how impossible they found writing Star Trek's "perfect people" to be.
As an animated half-hour comedy n0t set aboard the Starship Enterprise, Star Trek: Lower Decks gave itself the freedom to bend Star Trek's rules for humorous effect, and Mariner directly challenged Gene Roddenberry's rule in Lower Decks' season 2 premiere, "Strange Energies." When Mariner's holodeck workout program is interrupted by Jennifer, an Andorian Ensign, Beckett turns to the Cardassian hologram in her fantasy and says, "I know we're not supposed to have interpersonal conflict but I really hate that Andorian." For longtime fans, it's shocking to hear the main character of a Star Trek series declaring they hate someone. Meanwhile, Mariner has had issues with Jennifer before. In Star Trek: Lower Decks' season 1 finale, Beckett told Jen to shut up after the Andorian called Mariner "a psycho" for leaving angry voice messages at Boimler over on the Titan.
To be fair to Star Trek: Lower Decks, Mike McMahan's animated comedy does celebrate Star Trek's tropes and ideals even as it stretches what the franchise can get away with. Captain Freeman and her crew - including Mariner - are proud to be part of Starfleet and wholeheartedly believe in what it represents. Still, Mariner will openly critique Starfleet's mistakes and failures, and no one in Star Trek repeatedly and defiantly bucks Gene Roddenberry's rule about "no interpersonal conflict" more than Mariner. In her defense, Beckett is easily riled when she sees injustice or stupidity. Mariner purposely remains an Ensign because of her disdain for the command crew and to take advantage of the freedom low rank gives her to perform off-the-books solo missions as she sees fit. Mariner also argued constantly with Boimler, who is far more by-the-book.
Mariner's regular physical and verbal altercations with her fellow crewmates would never fly on the Enterprise, and they do often land Beckett in the Cerritos' brig. Of course, getting along respectfully on TNG didn't mean that every character necessarily liked each other - as a Klingon, Worf (Michael Dorn) never hid his feelings of animosity towards anyone. Mariner prides herself on not being one of Star Trek's "perfect people" yet she is bright, heroic, and irable in her own right. As for Jennifer, it's a clever move by Star Trek: Lower Decks to introduce the Andorian since she and Mariner amusingly share a mutual dislike. Still, it's hard to imagine anyone aboard Captain Picard's (Patrick Stewart) Enterprise openly professing to hate a fellow Starfleet Officer the way Beckett Mariner does on Star Trek: Lower Decks.
Star Trek: Lower Decks season 2 streams Thursdays on Paramount+.