Farting

Flatulence or 'farting' was a bodily process that affected some species, involving the expulsion of gas.

Many people thought farting humourous. (TV: Revenge of the Slitheen)

Amongst humans
Farting was frowned upon by humans, due to its foul smell and loud noise. Many humans, though, thought farting humourous. (TV: Revenge of the Slitheen) Ingestion of food such as cabbage, (TV: Revenge of the Slitheen) and baked beans, (TV: The Bounty Hunter) could induce it.

Among the Raxacoricofallapatorian species
When members of the Slitheen family used Compression fields to fit themselves into human skin suits, it caused a condition called 'gas exchange' which was similar to farting but with a smell like bad breath. This was due to calcium decay as Raxacoricofallapatorians were a calcium-based species. (TV: Aliens of London / World War Three)

When Blon Fel-Fotch Passameer-Day Slitheen, in the form of Margaret Blaine, took Cathy Salt to the toilets to kill her, she noted her "little tummy" was "complaining" when she farted loudly. Soon after, when she farted after entering the toilet, Cathy remarked, "Sounds like we got here just in time.". (TV: Boom Town)

Other instances
Farting was still possible after death, as the living dead man Owen Harper discovered shortly after being brought back to life by the resurrection gauntlet. He mourned in advance his last fart, saying that, along with sex, he'd miss it. (TV: Dead Man Walking)

When Victor Kennedy absorbed Bliss, her face ended up on his right buttock. When Elton Pope asked where she was, Kennedy lifted himself up, farting as Bliss told him he didn't want to know. (TV: Love & Monsters)