CRC cards is an activity related to role-playing games and object-oriented design first mention in a 1988 article titled “On the cruelty of really teaching computing science” by Dijsktra.

when two or more team members want to rapidly sketch a number of different ideas for the design of feature of an object-oriented system they write down on index cards the names of the more noticeable classes involved in the feature. The cards are then fleshed out with lists of the responsibilities of each class and the names of collaborators.

Then its time to pick which ones are going to validate and which won’t. They do this by playing out a plausible scenario of the computation related to each idea, creating a fictitious dialogue.