Star Trek: The Next Generation season 7 featured Wesley Crusher (Wil Wheaton) becoming a Traveler, a role that comes with a unique set of powers. Wesley Crusher was a semi-regular character on Star Trek: TNG and served as acting Ensign on the USS Enterprise-D for the first four seasons of the show, before joining Starfleet Academy and appearing less often in later seasons. After dropping out of the Academy in season 7, Wesley finally found his destiny and joined an organization called the Travelers, a mysterious group whose existence had been previously teased throughout the franchise.
While not much is known about the Travelers' true nature, they were described by Wesley as a collective of individuals with special abilities who protected the flow of time. The Travelers and their assistants, the Supervisors, helped ensure the correct progression of time by watching the timeline and dispatching agents to enact changes when needed. Wesley joined the Travelers after a few encounters with an alien who simply called himself The Traveler (Eric Menyuk) during Star Trek: TNG. The Traveler recognized Wesley's potential upon their first meeting and helped nurture his budding powers during subsequent encounters.
