I agree with Jooles, I think you've more or less covered it with that.
Other ideas might be pets or a favourite place. I think it just needs to be something he enjoys talking about, they probably don't really need the information.

They'll just be looking for his personality really I should think - though it's not always easy to capture this truthfully on a casting video as it's such an artificial thing to do! Can you give us an idea what it is for (without giving too much away) - e.g. is it for a TV show/quiz/game or is it for a film or TV drama?
Did they give any advice on length?