Oyster Card

Klyde Cheerman the cheer-up robot was wondering why the reusable transit pass for London was called an 'Oyster Card' 

He tried to imagine someone thinking of a name. 

Oi it is an Oyster card. Named after an animal that stays in one place all of its life. 

They should call it a falcon card or cheetah card or a fox card. Name it after an animal that moves around a lot at high speed!