On topic, and slightly in response to G: I remember seeing a performer on television (numerous shows, actually) swallow and regurgitate billiard balls (could have been ping pong balls--all I know is that they were white and round, heh), and also goldfish (totally unharmed). He would regurgitate the goldfish either head or tail first, it was up to the audience. He would also do other "interactive" things like that, swallowing things and regurgitating them in a specified order, for example. It was weird, but slightly entertaining.
Fun fact: His story for why he did it was because he'd have to swallow and then regurgitate his money/etc because he (I think) was in an orphanage (or lived in a bad area of town, had a bad school, or whatever...I forget exactly). Either way, the main thing is that it was to protect his valuables. Why do I mention this? It's nice to see a believable story to go along with the performance. It makes something weird like swallowing and regurgitating items make sense (at least, somewhat). Magicians and mentalists alike should take note of that.