Ceiling slime
From Tardis Wiki, the free Doctor Who reference
Ceiling slimes were a green species of a slime-like consistency that regularly excreted green balls of slime.
During the 2254 Dalek invasion of Earth, several ceiling slimes had taken over the London sewers, with one dropping slimeballs directly in front of a trapped hostage. During this invasion, the Seventh Doctor and two Daleks travelled past many ceiling slimes attached to the top of the London sewers. (GAME: Dalek Attack)
