'Chuck': Rebecca Romijn joins Season 5, is out to get Team Bartowski

"Chuck" has just increased its "beautiful blonde secret agent" population by one.

The NBC series, which begins its final season Oct. 21, has signed Rebecca Romijn -- Mystique in the first three "X-Men" movies -- for a guest role as a rogue CIA agent named Robyn Cunnings, EW reports. The character is described as cold, calculating and enamored of harsh interrogation techniques.

Robin and a group of fellow agents are also apparently not happy about Chuck (Zachary Levi), Sarah (Yvonne Strahovski) and Co. having taken their spy operation to the private sector. They hatch a plan to frame Chuck for a very serious crime.

Romijn currently stars in the Adult Swim comedy "NTSF:SD:SUV." Her other credits include "Ugly Betty," "Pepper Dennis" and "Eastwick"; she also had a brief cameo in "X-Men: First Class" as an older version of Mystique (played by Jennifer Lawrence).

What do you think of the casting?