Sarah Jane Smith (Elisabeth Sladen)

Sarah traveled with the third and fourth incarnations of the Doctor encountering Daleks, Cybermen and many other monsters. However, when the Doctor was summoned to Gallifrey, Sarah ended up getting dumped in South Croydon. Thirty years later she met the Tenth Doctor whilst investigating a school. When the Doctor left, he hid two gifts inside K9 Mark IV, which was Sarah's sonic lipstick and a watch that scans for alien life. She has committed her life to investigating alien encounters as well as being a mother to her newly adopted son Luke.

Maria Jackson (Yasmin Paige)

Maria Jackson is a 13 year-old girl who lives opposite Sarah Jane Smith. She's new to the area having only recently moved in with her single dad Alan. She discovered about Sarah's interest in exterrestrial life forms after seeing an alien in Sarah's garden late at night. She helped Sarah close down the Bubble Shock! factory and also helped a young boy that the Bane had created escape. This boy became Luke Smith.

Luke Smith (Thomas Knight)

Luke Smith or "The Archetype" was created by the Bane from thousands of samples of people visiting the Bubble Shock! factory. He contains the strengths and weaknesses of all the scanned visitors and an exceptional eidetic memory. However, he has no knowledge of manners or social behaviour and often says what he thinks because he doesn't know that it is wrong. After Luke was rescued from the Bane, he was adopted by Sarah Jane and now lives with her in her house.

Clyde Langer (Daniel Anthony)

Clyde attends the same school as Maria and Luke and discovered that aliens exist when he followed Maria into the school technology block and saw several Slitheen (including a child Slitheen) change out of their disguises. While Sarah Jane was annoyed to have another person depending on her she eventually warmed to Clyde when he proved helpful in figuring out the Slitheen's weakness and in defeating the family.

OTHER

CHARACTERS

Mr Smith - Sarah Jane's super computer

Alan Jackson - Maria's single dad.

Chrissie Jackson - Maria's nosey divorced mum

Kelsey Harper - A hyperactive Bubbleshock addict.