Rahnius

Ambassador Rahnius, or Rahni as he was called by his friends, was an ambassador for the Galactic Alliance. His identity (and likely his skin) was taken by a member of the Slitheen family to fool Sarah Jane Smith.

History
Rahnius arrived at Sarah Jane's house via teleport and offered a set of Deeley Boppers to the group as reward for their efforts in saving the Earth. His real identity as a Slitheen was exposed when the infamous gas exchange problem plaguing the family's skin suits caused abundant flatulence. He pretended he didn't know the name of his homeworld, which Luke Smith corrected him on. K9 soon teleported into Sarah Jane's attic and almost gave away his alien form, but Rahnius disabled him with a vehicle clamp. By now, it was a futile effort to keep up the charade. The Slitheen unzipped his skin suit disguise and activated his "Deadly Deeley Boppers" to root Sarah Jane and the children to the floor. He told the group that he had come to their attic to steal K9. With his extensive knowledge of the past and the future, no bank in space would be safe from him. However, Sarah Jane produced her sonic lipstick from behind her back and Clyde Langer threw a top hat at Mr Smith's control panel, knocking a lever backward that activated Mr Smith's energy reversal beam. He directed it into Sarah Jane's sonic lipstick and they turned the power of the Deeley Boppers against "Rahnius", immobilising him. Sarah Jane had Mr Smith send him back where he came from, along with K9's clamp. Sarah Jane warned him not to forget he had been bested by, as he put it, "a woman and a group of kids." (TV: From Raxacoricofallapatorius With Love)

Behind the scenes

 * Rahnius makes note of the fact that he and Rani Chandra share the same first name, uttering the phrase, "the two Ranis". This is a reference to The Two Ronnies, the famous comedy series that starred actor Ronnie Corbett, who portrayed Rahnius.