Ashley Tisdale has joined the cast of Patricia Heaton's new CBS sitcom, "Carol's Second Act." "I'm so excited to welcome @ashleytisdale to my new show , #CarolsSecondAct on @CBS! So talented, so sweet, so funny, so normal!" Heaton tweeted Friday about the former "High School Musical" and "The Suite Life of Zack & Cody" star. Heaton, who is best known for her work in the family comedies "The Middle" and "Everybody Loves Raymond," will play a retired teacher who decides to become a doctor. Deadline.com said Tisdale is replacing Bonnie Dennison, who co-starred in the pilot as Jenny, a pharmaceutical representative and the title character's daughter. No reason was given for the casting change. The show will also co-star Kyle MacLachlan, Ito Aghayere, Jean-Luc Bilodeau and Sabrina Jalees.