...They're commonly said to feed on parasites found in the mouths of crocodiles. According to Wikipedia, this is probably a myth. Are they right?

From my reading it does appear to be true. This kind of relationship is called a symbiotic one in which both parties benefit in some way.

Here are some more examples of such relationships-makes a fun and interesting read!

http://webecoist.momtastic.com/2009/03/ … tionships/