The sexy Irish-American Olivia Wilde. Olivia Wilde and Jennifer Morrison at the 100th Episode Party of their popular FOX medical drama series 'House' in Los Angeles Although she portrays a sexy brunette in House, Olivia Wilde is a natural blonde. Wilde's most famous role as a blonde was in The OC, where she played bartender Alex Kelly, the bisexual love interest of Mischa Barton's character