Peter Killian Gallagher (born August 19, 1955) is an American actor, musician and writer. He is best known for his roles as Sandy Cohen in the television drama series "The O.C." from 2003 to 2007, as Deputy Chief William Dodds on ", " Stacey Koons on the Showtime comedy-drama "Californication", and Nick on the Netflix series "Grace &amp; Frankie".