Potato

Potatoes were a vegetable on Earth, often used to make foods such as chips and crisps.

The Doctor was once imprisoned in the Tower of London with Sir Walter Raleigh, who kept going on about the potato, which he'd discovered. (DW: The Mind of Evil)

Peri Brown once found herself in a dimension modelled upon a combination of the Alice in Wonderland book she had been reading and the salad she had been eating. Among the creatures she met in this world were the King and Knave of Spuds, a pair of talking potatoes who nearly executed Peri for the heinous crime of eating vegetables. (DWM: Salad Daze)

The Sontarans were said to look like potatoes on several occasions. (DW: The Two Doctors, The Sontaran Stratagem, SJA: Eye of the Gorgon, The Last Sontaran)

After Gwen and Rhys hid in a truck filled with potatoes to escape to London, Gwen said "Rhys, you are not eating uncooked potatoes", after Rhys had asked her for a knife. (TW: Children Of Earth: Day Two)

In 2075, the First Doctor, John and Gillian used potatoes as makeshift weapons to defeat the space pirates on Anastas Thrax's space station. (TVC: The Hijackers of Thrax) Later, in 1800, the Tenth Doctor similarly used potatoes in combat. Onboard an American schooner in the Caribbean Sea during the dying days of the Quasi-War, he used potatoes, turnips and molasses to create an organic mixture capable of clogging proton cannons. (DWBIT: Second Wave)