Plot: Dave returns from an eight-week hiatus with a full beard and his writing staff intact; an audience Q&A bit is interrupted by Bill Scheft; ten striking writers present the Top Ten; Robin Williams discusses his recent USO trip to Iraq; after a 16-year layover, "Hal Gurnee's Network Time Killer" returns to the Late Show; associate producer Nancy Agostini appears on "Know Your Staff"; Lupe Fiasco performs "Superstar. "