If we're talking about what to stick in your holes (now girls don't let your imagination get the better of you I am talking about your crocs!) - I've just come across these more expensive charms similar to jibbitz:
Not sure what I thought and how they were made so looked them up to get more info - may be more secure and smarter, but are they in the essense of jibbitz? I don't know. What do you all think?
http://www.foyo.com.au/howdotheywork_foamshoe.htm
and fancy calling crocs - foam shoes - what ever next - I'm definitely off them now!!!