Helmar Augustus Cooper is an actor who played Gordon's father Grandpa Bill in Sesame Street Episode 3578.
Cooper has appeared in the Law & Order franchise, initially as one-shot characters and then recurring as judges on the original series (Judge McNeil) and SVU (Judge Reginald Flowers, three times). He performed on Broadway in several revivals including Oh, Kay!, South Pacific, Saint Joan, Ma Rainey's Black Bottom (understudying Carl Gordon), and Three Men on a Horse. Other TV credits include guest roles on Luke Cage, The Leftovers, Person of Interest, Boardwalk Empire, and The Job. Films include The Preacher's Wife (with Denzel Washington and David L. Smyrl), Addicted to Love (with Maureen Stapleton), Bloodhounds of Broadway (with Julie Hagerty), and Frankenhooker.