Best interview I ever had involved light bulbs (this is only a slightly related anecdote). My university application interview (for an electronics degree) cons

Best interview I ever had involved light bulbs (this is only a slightly related anecdote). My university application interview (for an electronics degree) consisted of a professor sitting in an office and asking "ok, lets talk about light bulbs. First tell me some interesting stuff about them". I promptly forgot everything sensible to say about light bulbs but with a bit of prompting and some reminders we had a reasonable conversation - he even got up and taught me stuff on a white board. At the time I though it went really bad but in the end his recommendation was a glowing one and I got the place. When I revisited this memory a little while ago (when writing some questions for an interview I was conducting) it occurred to me that actually it was one of the best interviews I've ever been too. The subject material didnt matter too much at all (except that it was well within the limits expected of me) but it tested everything they wanted to know about me: subject recall, willingness to learn, interest in the subject, ability to actually understand the material etc. They also got us to take a calculator apart as a group and talk about with a professor. All simple stuff but the same principles applied (I enjoyed that part a lot more :D)