Dexter and 24 will get two new characters on their upcoming seasons – John Lithgow has been cast on “Dexter,” while Freddie Prinze Jr. is joining the cast of “24.”

John Lithgow is set to appear in all 12 episodes of Dexter’s fourth season – he’ll play ” mild-mannered suburbanite” serial killer Walter Simmons, a new nemesis for Dexter (Michael C. Hall)!

Dexter kicks off season 4 on September 27.

In other casting news, Freddie Prinze Jr. will join the cast of “24,” playing Davis Cole, “a recently returned Marine who runs CTU Field Ops and wants to follow in Jack Bauer’s (Kiefer Sutherland) footsteps.”