exercises in future shock

I was thinking about aspects of modern American culture that even someone from a very recent time period would find difficult to understand, and was struck with the following idea for a science fiction writing exercise:

Write a scene where a time traveller from the 21st century attempts to explain cat macros to a person from the 1980s.

Credit where credit's due: I'm pretty sure this came out of a conversation with icebluenothing over espresso at my place.