It's definitely fun to throw out some random questions and see what she comes back with. It's more amusing than useful...but I have been asking her to remind me about appointments with a high rate of success!
I didn't think it was possible to change Siri's voice since Apple doesn't offer any official "themes" to mess around with but you can play around with the language settings for a little bit of fun. Just go to Settings/General/Siri/Language. There are a few English options there to try out and if you select English (United Kingdom) she switches to a male voice with a British accent.