The Hollywood Reporter says the pilot is from producers Shane Black and Joel Silver.
Cassidy is best-known for his portrayal of a teen detective on the television series, "The Hardy Boys Mysteries."
In other casting news, the trade paper noted Jason O'Mara has landed a lead role on Graham Yost's ABC drama, "Countdown."
Miguel Sandoval and Jake Weber have been tapped to star opposite Patricia Arquette in NBC's "Medium," Paul Blackthorne has been cast in ABC's "Gramercy Park," D.W. Moffett and Noelle Beck have been hired to play the parents in Fox's untitled family pilot. "Jake 2.0" star Christopher Gorham has been signed to co-star opposite Neal McDonough in NBC's untitled medical mystery pilot, and Jon Seda has joined Taye Diggs on UPN's "Kevin Hill."
UPN has also added "Second Time Around," a comedy top-lined by Boris Kodjoe and Nicole Ari Parker, while NBC has given the green light to "Beverly Hills SUV," a comedy from "Bernie Mac" creator Larry Wilmore.