bad breath, which the Doctor noted was a form of calcium decay—though, in reality, bacteria that cause tooth decay are different from those that cause bad breath). This side-effect is also overcome by the newer technology in The Lost Boy. Gas exchange When the Slitheen are in their skin suits they break wind loudly; they call this the gas exchange. This can also be caused by over-eating. In The Gift, Sarah Jane and the gang destroy their source of food, a plant called Rackweed, which is native to Raxacoricofallapatorius. The Rackweed, when digested, is in their stomachs. Using the audio of every audio producing device in the vicinity, Mr Smith triggers a sound in the attic. This causes the Slitheen-Blathereen aliens to start farting uncontrollably and through the subsequent vibration of the sound and of their own farts, cause their stomachs to explode. Clyde then says that the Blathereen aliens had "farted themselves to death." Vulnerabilities Raxacoricofallapatorians are vulnerable to acetic acid, which reacts explosively—and fatally—with their bodies, making Slitheen allergic to vinegar, ketchup and Coca-Cola. One of the Raxacoricofallapatorian methods of execution is the lowering of the condemned into a cauldron of acetic acid, which is then heated to boiling. The acidity of the solution is formulated to dissolve the skin, allowing the internal organs to drop into the liquid while the condemned is still alive, reducing them to "soup" in a slow and painful death. In "World War Three", when a single Slitheen was electrocuted, the effects were transmitted to other Slitheen, even those across the city. Appearances When they first appeared in "Aliens of London" (set in 2006), the Pasameer-Day branch of the Slitheen had been in Great Britain for some time, having infiltrated various levels of British society, from community leaders and military personnel to mid-level politicians and government officials. Their intent was to instigate World War III and sell the radioactive remains of Earth to a depressed galactic economy as fuel for interstellar spacecraft. They staged the crash landing of an alien spaceship in central London, setting up a cybernetically augmented pig as an "extraterrestrial" body. With the world in a state of heightened alert and panic, and with their commander Jocrassa assuming the role of Acting Prime Minister, they persuaded the United Nations to allow the United Kingdom to use its nuclear arsenal against the alien "massive weapons of destruction". Before the Slitheen could