On a lighter note, both Summer Glau and Tricia Helfer guest starred on Chuck.
Summer Glau played Greta 4.0 in Chuck s04ep08 "Chuck Vs. The Fear of Death" that originally aired November 15, 2010.
Summer's role was part of the B-plot :
John Casey and Morgan Grimes try to protect Jeff Barnes and Lester Patel from the truth when they snoop around to find out the true identity of Greta (Summer Glau).
Tricia Helfer played Agent Alex Forrest in Chuck s02ep18 "Chuck Vs. The Broken Heart" that originally aired on March 30, 2009.
Tricia's role was part of the A-plot :
Tricia Helfer guest stars as agent Alex Forrest, assigned to evaluate Sarah's performance due to General Beckman's concerns about her relationship with Chuck.
For those who think that Summer was used as eye-candy in Chuck, they should watch Tricia in sexy outfit teasing Captain Awesome.