Because the word bum has an alternate meaning in the United States, the book titles were changes to use butt instead. The third book is further renamed to Butt Wars: The Final Conflict.
Griffiths' reference guide to "prehistoric bumosaurs", What Bumosaur Is That?, was published in May 2007. It is not a part of the trilogy, although the book was mentioned in the trilogy.
Mills, Alice (2008), Behind the bum : A psychoanalytic reading of Andy Griffiths' Bum trilogy, Deakin University, School of Literary and Communication Studies, ISSN1034-9243