Note: To help refresh your memory, wiki links are provided for characters when available.
Chuck - "Chuck Versus First Class"
"Stone Cold" Steve Austin guest starred as 'Hugo Panzer,' the Ring operative that 'Chuck' was assigned to take down on the plane. Obviously, he's recognizable from wrestling.
House - "Remorse"
Shane Edelman guest starred as 'Bill,' the husband with the psychopathic wife. Terminator: The Sarah Connor Chronicles fans may recognize him as 'Matt Murch,' who was assigned to work with 'John Henry.'
Castle - "The Third Man"
Better Off Ted - "Mess Of A Salesman"
Eddie McClintock guest starred as 'Billy Crisp,' Ted's brother, who he helped get a job as a salesman. Warehouse 13 fans will recognize him as 'Pete Lattimer.' He has also appeared on Bones as 'Special Agent Tim Sullivan.'
Human Target - "Embassy Row"
Emmanuelle Vaugier guest starred as undercover FBI Agent 'Emma Barnes.' Smallville fans may recognize her as 'Dr. Helen Bryce.' She has also guest starred as 'Madison' (a werewolf) in an episode of Supernatural, and she has appeared in Saw II and Saw IV.
Dollhouse - "Epitaph Two: Return"
Adair Tishler guest starred as 'Caroline,' or at least an imprint of the original, which you saw happen if you watched "Epitaph One" via the season one DVD, iTunes download, or Amazon.com VOD. Heroes fans will recognize Adair as 'Molly Walker,' the hero that had the ability to locate anyone.
Click here to to see picture of Adair with some of the cast from Dollhouse.