Hi There, Alan Smithee is referred only to a director that has their
name removed from the credit block. The alias George Spelvin is used
by actors,  chiefly for the theater, who don't want their name known
or who haven't yet been confirmed for an engagement and a name needs
to go into  the program. Ciao, Alison
 
----
Online resources for film/TV studies may be found at ScreenSite
http://www.tcf.ua.edu/screensite