Sebastian Saga was the villain in "A Thing For Musicians". An elderly, musically themed villain, Sebastian was once a famous guitar player, but a pyrotechnical stage accident severely injured the left side of his body and destroyed his left arm, leaving him bitter and unable to play the guitar. He has a metal prosthesis for a left arm, and a haircut that conceals the left side of his face.
In "A Thing For Musicians", Sebastian is introduced as the manager for fledgling rock star Ricky Mathis. Sebastian planned to play hypnotic music during Ricky's music concert in order to hypnotize the crowd into attacking the world's governments. However, the spies confronted Sebastian at the concert and foiled his plans, forcing him to attempt an escape in his personal helicopter. The spies turned Sebastian's own trick against him by targeting the helicopter with a wind tunnel hair dryer pushing the helicopter into the transmitter playing the hypnotic music, enabling the capture of Sebastian.
In "Stark Raving Mad", Sebastian escaped from Prison and returned intending to get revenge on the girls by sabotaging local raves with hypnotic music that made people go beserk and start riots. Sebastian used his raves to destroy the spies' favorite places such as the: Roller Disco, Modern Art Musuem, and the Beverly Hills Mall. After telling the girls his plan, he attempted to destroy Beverly Hills High. He was foiled once again.
- The helicopter used is the Mil Mi-24.
- Sebastian Saga's rave music is used.
- He is the villian in "Operation Tami Trouble" in "The Amazing Spiez".
- Every time Sebastian makes an appearance on screen, his signature rock music track is played in the background.
- He is the first villain of the series. This was changed after "Totally Spies! The Movie" aired.