Interviewing yourself

Jeremiah McDonald filmed himself as a twelve-year-old as though he was talking to himself in the future.  His 32-year-old (and rather more cynical) self responds to the questions - or does he?  Who's interviewing who here, and how was this done exactly?  Some smart editing and some clever shifting of viewpoint make this a delightful video to check out.  

And if that doesn't impress you, how about being amused by Mitchell and Webb's take on a homoeopathic Emergency Department?