Mia Challis has joined the CBS multi-cam comedy pilot “Regency,” Variety has learned. Challis joins previously announced cast member Rhys Darby in the pilot, which originally ordered back in December. The official logline describes it as “a historical spin on the classic multi-cam family sitcom, centered around the upper-middle class Tillbrooks as they navigate life, love, and scandal in 19th Century England.” Challis will play Wilhelmina Tillbrook, who is said to be “the Tillbrook’s youngest