http://www.nme.com/news/pixies/46231
"(Bam Thwok) was all ostensibly for a submission to a film which shall remain unnamed"

http://www.nytimes.com/2004/08/08/arts/music/08PARE.html
"The Pixies have recorded a new song together, written by Ms. Deal, called "Bam Thwok," which was originally written for the soundtrack to "Shrek 2.""