How about Lewis Black showing up for three seconds?
Eriq La Salle (ER's Dr. Benton) and Ving Rhames (Marsellus Wallace of Pulp Fiction) play two of Jacob's fellow veterans, before either of their actors had those roles.
Jason Alexander also has a small role.
When Jacob is running a high fever and freaking out, Kyle Gass helps fill his tub with ice.
