Pickford's Water Bottle

Using pre-written prompts or cheat codes to help you perform well at something like an exam, speech, GTA or penalty shootout. Potentially written on your hand, sleeve, scrap of paper or water bottle.

Jenkins: "What ho Pembo!"
Pembo: "What ho!"
Jenkins: "I say Pembo, how did you manage to ace that Latin exam? You never study."
Pembo (tapping the side of his nose): "Pickford's Water Bottle, Old Chap!"