"Those Old Scientists" is the seventh episode of the second season of the television series Star Trek: Strange New Worlds and was released on Paramount+ on July 22, 2023. In this crossover episode, characters from the animated series Star Trek: Lower Decks are sent back in time to the 23rd-century setting of Strange New Worlds. Captain Christopher Pike and the crew of the USS Enterprise (NCC-1701) have to work with Ensigns Mariner and Boimler to return them to their proper time.

"Those Old Scientists" was written by a combination of Lower Decks and Strange New Worlds writers and directed by longtime Star Trek actor and director Jonathan Frakes. Lower Decks voice cast members Tawny Newsome and Jack Quaid play their characters in live action for the first time; the cast and crew paid special attention to translating their animated portrayals to a more realistic medium. The episode was positively received by critics, who praised the humor, acting, and celebration of Star Trek as a franchise.

In the 24th century, an away team from the Federation starship USS Cerritos arrives at the planet Krulmuth to perform routine scans on a portal found there. While Ensign Brad Boimler excitedly says that it was discovered by the crew of the USS Enterprise, led by Captain Christopher Pike, D'Vana Tendi insists it was found by an Orion vessel that her ancestor was stationed on. When Boimler has his picture taken at the portal, it unexpectedly activates and he is sucked through to the 23rd century, meeting the Enterprise crew.

While the crew tries to figure out how to send Boimler back to his time, Boimler tries (and fails) to avoid divulging knowledge of future events, nervous around the historical figures he considers heroes. An Orion ship arrives in orbit; Boimler convinces Captain Pike not to fire on the ship, but the Orions beam the portal from the surface and warp away. Boimler helps the crew track the Orions, and they trade the grain supplies destined for a colony they were carrying in exchange for the portal. The Enterprise crew transports the portal back to Krulmuth. Before Boimler can step through, Ensign Beckett Mariner emerges from the other side, exhausting the portal's power supply and trapping them in the past.

Boimler and Spock fail to synthesize more of the portal's power source, the rare material horonium, while Mariner talks with Nyota Uhura, her idol, and convinces her to take a break from always working to have some fun. Enterprise engineer Pelia informs Boimler of the irreplaceable nature of the grain they traded to the Orions, and a remorseful Boimler tries to contact the Orions and steal a shuttle to get it back. After Boimler and Mariner are detained and talk with Pike, Boimler realizes there is another source of horonium on Enterprise—a piece of the previous ship to carry the name built into the current vessel. On the surface of Krulmuth, the Starfleet officers encounter the Orions, who received Boimler's signal. Pike explains the situation, and Boimler mentions that, in the future, Orions are no longer seen as dishonorable pirates and that one of their friends is an Orion. Pike says they want to send Boimler and Mariner home and, in exchange, suggests that history remember Orion scientists discovered the portal; the Orion captain happily agrees. Boimler and Mariner successfully return to the future.

Crossover episodes between Star Trek shows have happened infrequently in the franchise's history, generally limited to guest character appearances on other shows. The Star Trek: Strange New Worlds team approached Lower Decks creator Mike McMahan with the idea of a crossover; McMahan was enthusiastic, as the animated Lower Decks characters were designed to resemble their voice actors. Initially, the plan in early drafts of "Those Old Scientists" was that the episode would be mostly focused on Boimler, but through rewrites Mariner's character took on a larger role.

"Those Old Scientists" was written by Kathryn Lyn and Bill Wolkoff, and executive produced by Henry Alonso Myers and Akiva Goldsman. It was directed by Jonathan Frakes, who plays William Riker in the franchise; the episode was his 222nd episode of Star Trek. Frakes did not campaign for the job but felt that he was picked because of his experience acting on Lower Decks and directing Strange New Worlds. Seasons 1 and 2 of Strange New Worlds were shot nearly sequentially amid the COVID-19 pandemic, leading to what Frakes called a frequently "grueling" pace, but he said he was "thrilled" for the opportunity to make a full-on comedy. Much of the episode's humor derives from franchise in-jokes; the episode title derives from a joke in the first season of Lower Decks that the fan acronym for the original 1960s series, TOS, stands for "Those Old Scientists".

Lower Decks voice cast members Tawny Newsome and Jack Quaid portray their characters in live action. Newsome and Quaid were allowed to improvise some of their dialogue. While Quaid and Ethan Peck (Spock) knew each other and developed a rapport on set, Newsome pushed for her character to interact with Uhura, believing the contrast between the buttoned-up Uhura and the "chaos" of Mariner held comedic potential. Quaid studied his animated character for cues on his acting, including a distinctive speed walk. Newsome, meanwhile, decided Mariner was simply herself but more animated. Both had input on their character's looks, with Newsome insisting Mariner have curls. Quaid wore a wig in a toned-down purple compared to his animated character; he considered dyeing his hair but thought that would tip off fans about the crossover before it was announced. The Lower Decks uniforms were recreated for live action in a darker shade so they contrasted less with the costumes for the series regulars. In addition, Lower Decks actors Noël Wells (Tendi), Eugene Cordero (Rutherford), and Jerry O'Connell (Ransom) have brief speaking appearances as their characters. As an in-joke, Ransom makes a lewd comment about Number One, who is played by O'Connell's real-life wife Rebecca Romijn.

At San Diego Comic-Con on July 23, 2022, Paramount announced that the second season of Strange New Worlds would have a crossover episode with Lower Decks. Quaid clarified that he and Newsome would be playing their characters and interacting with the Strange New Worlds cast primarily in live action, as opposed to a Who Framed Roger Rabbit–style blend of live action and animation. McMahan originally wanted the crossover to remain a surprise, so that unexpecting viewers would cut from the normal opening titles to the animated first scene. The episode premiered at Comic-Con on July 22, 2023, followed shortly by a release ahead of the show's usual schedule on Paramount+. The episode released on home video formats as part of the second season on December 5, 2023.

Reviews of "Those Old Scientists" were positive. IGN called the episode "an instant classic", while Comic Book Resources and TrekMovie called it the funniest episode of the series thus far. Keith DiCandido wrote that the episode functioned well as an episode of Lower Decks or Strange New Worlds, as well as being a great episode of Star Trek generally. Lacy Baugher of Den of Geek wrote that the humor might not land for every viewer but felt that the show should be applauded for taking creative risks. The Verge's Alex Cranz said that even at the episode's most silly, it felt like a proper episode of Strange New Worlds and not a "weird and forced" crossover.

Critics found the comic tone of Lower Decks meshed with that of Strange New Worlds and demonstrated the increased variety of storytelling the Star Trek franchise employed. Baugher and Vulture's Keith Phipps said that while on paper the different tones of the shows should not have worked well together, in practice the episode made the combination look easy, relying on the commonalities of optimism and heart. DiCandido thought the shift to live action made Mariner a less annoying character.

Critics noted that the episode served as a celebration of Star Trek more broadly, with Baugher calling the episode a "love letter" to fans. The Escapist's Darren Mooney opined the episode had been too reverential and nostalgic for previous Star Trek media while also lacking dramatic stakes. In comparison, Variety's Adam Vary wrote that the episode never "curdle[d] into fan worship" and proved an effective examination of Star Trek's hold on fans.

The episode was a finalist for the 2024 Hugo Award for Best Dramatic Presentation (Short Form).

• "Those Old Scientists" at IMDb
• "Those Old Scientists" at Memory Alpha