Disguise Names: Jay and Heidi Stafford
Slitheen Names: Jay Slitheen and Heidi Slitheen
Played by: Jay Simpson and Holly Atkins
Home Planet: Raxacoricofallapatorius
Species: Raxacoricofallapatorian
More Information: Jay and Heidi Stafford are actually members of the notorious Family Slitheen disguised in their new, advanced slim-line flesh suits. Conspiring with an unknown alien called the Xylok, the Family Slitheen seek revenge as well as a profit. Further information on the Family Slitheen can be found in the Revenge of the Slitheen character guide here.

Name: Xylok
Voiced by: Alexander Armstrong
Home Planet: Unknown
Species: Xylok (crystal)
More Information: The Xylok is a crystal race which crashed to Earth as a meteor and were trapped underneath the surface of the Earth for thousands of years until the eruption of Krakatoa freed a tiny piece of the Xylok entity. Sarah Jane was able to obtain the piece for inspection where she found it could communicate with her laptop. By doing so it was able to create Mr Smith.

Name: Nathan Goss
Slitheen Name: Nathan Slitheen
Played by: Ryan Watson
Home Planet: Raxacoricofallapatorius
Species: Raxacoricofallapatorian
More Information: This is the same Slitheen who appeared in Revenge of the Slitheen, but is now disguised as Nathan Goss, but was earlier disguised as Carl. Nathan was helping Jay and Heidi to bring the Moon crashing down on Earth.