Shannon Purser: Shannon Purser. Actress: Sierra Burgess Is a Loser. Shannon Purser is an American actress, known to audiences for her roles in the series Stranger Things (2016) as Barbara "Barb" Holland, and CW's teen drama Riverdale (2017) as "Ethel Muggs". She was born on June 27, 1997, in Atlanta, Georgia, where she worked at a movie theatre. She switched her focus on a career in acting. After making her screen debut...