Fat cell

13 Paternoster Row was once attacked by fat cells animated by Gallos Flambo with the intent of uniting two warring empires before their peace talks could be signed. Based in the sewer, the cells infiltrated the house via the plumbing, but Vastra and Strax destroyed the intelligent centre with acid grenades. Strax thought the technology resembled that of the Rutan Host. (AUDIO: Dining with Death)

Behind the scenes
The technical name for a fat cell is an adipocyte.