"The Star Beast" marked the first full episode of David Tennant's Doctor Who return. Tennant famously portrayed the Tenth Doctor on Doctor Who, taking over as the Time Lord from Christopher Eccleston at the end of the first season of the sci-fi series' 2005 revival. Tennant's Doctor quickly became a fan favorite, infusing the Doctor with a far more upbeat and energetic personality than his predecessor, while maintaining moments of severe intensity. Following Eccleston's departure, the Tenth Doctor led the show for the rest of Russell T Davies' first era as Doctor Who showrunner, surviving into Season 4 and the specials that followed.
Source：https://www.cbr.com/doctor-who-tenth-fourteenth-doctors-differences/
