This thesis explores the intersections between repetition, leitmotif and the philosophy of Gilles Deleuze in the context the BBC television series Doctor Who (1963-1989; 2005- ). Deleuze proposes that instead of the return of the same, repetition, by its constant insertion in a new temporal context can produce difference as part of the process of the eternal return. He also rejects the concepts of being in favour of becoming. I argue his framework on repetition allows us to broaden the definition of the leitmotif and embrace the role of repetition. I analyse the leitmotif of three characters: Amy Pond, River Song, and the Doctor. In all three instances, the leitmotifs are an active participant in the process of becoming while, simultaneously, undergoing their own becoming. For River, the leitmotif also works as a territorializing refrain, while for the Doctor, use of leitmotif paradoxically gives the impression of being.