(written from a Production point of view)
David Walrod is an actor who played a Xyrillian in the Star Trek: Enterprise episode "Unexpected". He received no credit for this role and was identified by the name tag of his costume which was sold off on It's A Wrap! sale and auction on eBay. 
Among his acting resume are the films "Live Free Die Hard," (Bruce Willis) Win a Date with Tad Hamilton! (2004, with Patrick Fischler, and stunts by Freddie Hice, Lisa Hoyle, Diana R. Lupo, and Tim Rigby), The Break (2006), and Brokeback Karate (2006).