Elyes Cherif Gabel is an English actor. Among his most notable roles, he has portrayed Dr. Gupreet "Guppy" Sandhu in the BBC medical drama Casualty, Dothraki Rakharo in Seasons 1 and 2 of the HBO series Game of Thrones, and P.E. teacher Rob Cleaver in the BBC drama Waterloo Road. He appeared in the ITV drama Identity, and portrayed Detective Adam Lucas in Season 3 of Body of Proof. From 2014 until 2018, Gabel starred in the CBS series Scorpion as computer genius Walter O'Brien.