Longo was a Human Starfleet officer who was assigned to the USS Enterprise-D in 2364. In that year, Longo was a lieutenant. He began playing Parrises squares as an ensign.
He was among the group of Starfleet officers who visited the Bandi shopping mall at Farpoint Station during the Enterprise-D's visit. Later he passed the sickbay aboard the ship and was among the personnel leaving sickbay during the evacuation of the stardrive section. (TNG: "Encounter at Farpoint")
He was among the personnel leaving a room while preparing for the medical emergency on Quadra Sigma III. (TNG: "Hide And Q")
He was a member of the Parrises squares team of the Enterprise-D and prepared for a match together with Worf, Natasha Yar, and another female crewmember against the Starbase 74 team. Later, wearing his command red uniform, Longo passed Commander Riker and Doctor Crusher in a corridor. (TNG: "11001001")
Wearing a skant uniform, he was working on a computer panel in a corridor and was passed by Captain Picard, Commander Riker, and Admiral Gregory Quinn following the return of the ship back to Earth. (TNG: "Conspiracy")