Skin suit

Skin suits, alternately referred to as flesh suits, (TV: The Lost Boy) were disguises made of the skin of an individual.

The suits were used by several species. Among them were the Raxacoricofallapatorians. (TV: Boom Town) If the skin was smaller than the individual using it, there were different techniques to use. The Raxacoricofallapatorians used compression field collars. Initially, the range of wearable skins were limited to humanoids of large builds and had the side effect of frequent gas expulsion. (TV: Aliens of London/World War Three) In the early 21st century, compression field technology later advanced to the point where they could fit inside the skins those of thinner frames and life forms the size of footballs. The gas exchange issue was fixed. (TV: The Lost Boy, PROSE: The Monsters Inside)

Raxacoricofallapatorians such as the Slitheen typically created skin suits from individuals they had murdered. Alternatively, synthetic skin suits were in use by 3764, when Slist Fayflut Marteveerthon Slitheen wore one based on an image of the Ninth Doctor broadcast from Fluren's World to act as the star of Doctor Who?. (COMIC: Doctormania) It was still possible to have sex with the skin suit's species of origin; suggesting the technology can replicate the reproductive biology to an extent. A Slitheen posing as Oliver Charles noted he enjoyed the act with Mrs. Charles, a mistress and a farmer. (TV: Aliens of London)

The Foamasis were gifted with a biology that gave them hollow bones with double joints every few centimetres, a high liquid content, small organs and a retractable tail. (PROSE: Placebo Effect)

History
The Passameer-Day Slitheen wore skin suits made from members of the British government whom they had slain; Jocrassa Fel-Fotch Passameer-Day Slitheen was disguised as Joseph Green, Blon Fel-Fotch Passameer-Day Slitheen as Margaret Blaine, Sip Fel-Fotch Passameer-Day Slitheen as PC Strickland, one as Oliver Charles then R. Asquith, one as Tennant James, one as Ewan McAllister and one as Sylvia Dillane. (TV: Aliens of London/World War Three)

Though the Passameer-Day Slitheen were mostly destroyed by a harpoon missile, Blon survived (AUDIO: Sync) and continued to pose as Margaret Blaine for six months. While wearing the suit, Blon detached her arm to threaten Rose Tyler. Soon after, however, Blon was regressed back into an egg by the heart of the TARDIS. (TV: Boom Town) Returned to Raxacoricofallapatorius by the Ninth Doctor, Blon, renamed "Margaret", was raised as a Jingatheen and continued to wear the skin of Margaret Blaine. (COMIC: A Confusion of Angels)

Glune Fex Fize Sharlaveer-Slam Slitheen disguised himself using the skin of Greg Blakeman, Kist Magg Thek Lutiven-Day Slitheen as Tim Jeffery, Florm Rox Fey Fenerill-Slam Slitheen as Janine and Korst Gogg Thek Lutiven-Day Slitheen as Carl. They were joined by a further five Slitheen disguised as humans. (TV: Revenge of the Slitheen)

Korst later returned as Nathan Goss alongside Dax Fex Fize Slitheen and Bloorm Vungah Bart Slitheen who respectively wore the skins of Nathan's parents, Marco and June Goss, adopting the aliases Jay and Heidi Stafford. (TV: The Lost Boy, PROSE: The Lost Boy)

A child Slitheen confronted Sarah Jane using the skin of Ambassador Rahnius of the Galactic Alliance. (TV: From Raxacoricofallapatorius with Love)

Sarah Jane and her friends later intercepted a pair of Slitheen, one disguised as Chris and another as Dave. (TV: The Gift)

On Clix in the year 3764, the Ninth Doctor and Jack Harkness used synthetic skin suits to disguise themselves as Raxacoricofallapatorian. These skin suits were not harmed by the acid rain which proved deadly to real Raxacoricofallapatorians. (COMIC: Doctormania)