Lemon

Lemons were a citrus fruit on Earth. The planet Oroobia had the general scent of lemons when the Tenth Doctor and Donna Noble visited. (PROSE: The Doctor Trap)

The fruit, juice and peel of the lemon was used in foods and drinks. Lemon juice was often used to flavour tea and was preferred by Skullions to water as water "burned" them. (TV: The Man Who Never Was) Lemon peel was one of the ingredients in Kaiser pudding. (TV: The Enemy of the World) Lemon was also a key ingredient in lemonade. (TV: Dead of Night)

The Doctor
The First Doctor carried everlasting matches that gave off a lemon scent when lit. (PROSE: Venusian Lullaby)

The Third Doctor preferred lime to lemon in his Bombay Sapphire Gin when he drank with Iris Wildthyme. (PROSE: Verdigris)

The Doctor's TARDIS had lemon trees in the library. (AUDIO: The Settling) The TARDIS's "laundro-demat" could program scents into the clothes it washed, including Jacondan lemons. (COMIC: Laundro-Room of Doom)

The Eighth Doctor took his darjeeling tea with lemon. (PROSE: Fallen Gods)

There was a planet that the Tenth Doctor considered amazing, where lemons evolved into people and lived a harmonious existence with a breed of hyper-intelligent bee. (PROSE: Keeping up with the Joneses)

Other references
The Governor compared Bentley to a lemon meringue in that both were stiff and sour. (PROSE: The Blood Cell)

Behind the scenes

 * A lemon Jelly baby collectible card is one of 50 collectible cards released as part of The Adventure Games.