O'Grady will play Margo Cowan, one of the stars of the hit Real Housewives-esque reality show The Wives of Wall Street. The cameras follow her as she runs her cosmetics empire — an empire that employed the victim of a murder the team is investigating.
Aside from playing Blue's big-haired squad secretary Donna for three years, O'Grady is also known for her role as American Dreams' family matriarch. She most recently guest-starred on Hawaii Five-0 last year.
Castle airs Mondays at 10/9c on ABC.