Warning: SPOILERS for Star Trek: Lower Decks Season 1, Episode 6 - "Terminal Provocations"
In Star Trek: Lower Decks episode 6, the U.S.S. Cerritos transferred the worst Starfleet Officer aboard to the U.S.S. Titan, the starship led by Captain William T. Riker (Jonathan Frakes). The animated comedy series has reveled in Star Trek canon and made numerous mentions of various people, starships, and events throughout the 23rd and 24th centuries. But the end of Star Trek: Lower Decks' sixth episode is the first time the Titan has been canonically mentioned since Riker took command with his wife, Counselor Deanna Troi (Marina Sirtis), at the end of Star Trek: Nemesis.
In Star Trek: The Next Generation and the four TNG movies that followed, Commander Riker was the First Officer of the U.S.S. Enterprise-D and E under Captain Jean-Luc Picard (Patrick Stewart). Riker was a talented and respected leader who was considered to be on the fast-track to becoming Captain of his own starship. However, Riker infamously turned down a number of promotions, preferring to stay aboard the Enterprise as Picard's Number One. It took 15 years, but Riker finally decided to accept a long-awaited promotion to Captain; however, Picard still had no intention of leaving the Enterprise's big chair, and Riker (and Troi) were assigned to the U.S.S. Titan.
Star Trek: Lower Decks is set in 2380, a year after Star Trek: Nemesis, so Riker and Troi are just a year into their tenure aboard the Titan when the U.S.S. Cerritos sent them the worst Officer in Starfleet. Star Trek: Lower Decks episode 6, "Terminal Provocations", introduced Ensign Fletcher (Tim Robinson), an old friend of Ensign Brad Boimler (Jack Quaid) from Starfleet Academy. At first, Fletcher seemed like a helpful, stand-up guy who impressed Ensign Beckett Mariner (Tawny Newsome) and spoke of the goodness within every Starfleet Officer. But it soon became apparent that the self-serving Fletcher actually lacked this quality himself. After he volunteered to finish a task installing shield cores alone that he, Boimler, and Mariner were assigned to, Fletcher made up a cockamamie story of being attacked and knocked unconscious to explain why he didn't do the job like he promised. Fletcher not only lied, but he actually tried to upgrade his brain so he could be smart enough to finish the task; but instead, the shield core absorbed Fletcher's brain waves and became a sentient monster.
Fletcher's mechanical creation attacked the Starfleet Officers and threatened the ship but instead of helping Mariner and Boimler fight it, Fletcher preferred to concoct another lie that they were attacked by a renegade Q. However, the two Lower Deckers - with no help from Fletcher - blew the rampaging robot out of the Cerritos' airlock. Conveniently, the sentient machine attacked a hostile enemy vessel that was, in turn, attacking the Cerritos over the salvage rights to the derelict Starfleet debris floating in outer space.
Fletcher's monstrosity actually ended up saving the Cerritos and, since this is Star Trek: Lower Decks, Fletcher was rewarded with a promotion and a transfer to a "better" starship, Will Riker's U.S.S. Titan. However, the crew of the Titan quickly realized that Fletcher is an incompetent idiot; he was "fired" from the Titan only six days later and sent back to Earth. This time, Mariner and Boimler didn't stick out their necks to help Fletcher, who had no place aboard the Cerritos, much less the Titan.
Although Riker and Troi appeared in Star Trek: Picard, which was set in 2399 - almost 20 years from Star Trek: Lower Decks - they didn't specifically mention their time on the U.S.S. Titan by name. Instead, it was merely inferred that the Rikers left their last starship posting and moved to Nepenthe, hoping the planet's regenerative properties would help their terminally ill son Thad. And when Riker returned to Starfleet to save Picard, he took command of the U.S.S. Zheng He instead. But Captain Riker was in command of the Titan during Star Trek: Lower Decks and clearly, he maintained the same high Starfleet standards that were found aboard the Enterprise so that a fool like Ensign Fletcher couldn't last aboard Riker's Titan.
Star Trek: Lower Decks streams Thursdays on CBS All-Access.