Junior navigator aboard the U.S.S. Enterprise in the early days of Captain Kirk's command. During a tense confrontation with the First Federation flagship Fesarius, Bailey erupted in several emotional outbursts while serving on the Bridge, drawing rebukes from First Officer Spock. To help him grow as an officer, Captain Kirk brought Bailey along on an away mission to the Fesarius, where they met the actual commander of the ship, the child-like Balok. When Balok offered to engage in a cultural exchange with the UFP, Bailey gladly agreed to remain on the Fesarius as an emissary, and developed a taste for Tranya in the process.