Will Ferrell has joined the cast of Paramount Pictures’ “Zoolander,” which starts shooting today.Scott Rudin Prods. and Ben Stiller’s Red Hour Films are producing the fashion-themed comedy. Stiller is writing, directing and starring, along with Owen Wilson. Ferrell plays Mugatu, a flamboyant fashion designer and rival of Stiller’s character. Ferrell is repped by United Talent Agency and managed by the Gold-Miller Co.