The line comes from The Room, Tommy Wiseau's 2003 independent drama, where Tommy greets his best friend Mark, played by Greg Sestero, on a rooftop. The film's earnest acting and unusual dialogue turned it into a cult favourite, with midnight screenings and fan quoting keeping its most famous lines alive. Oh hi, Mark became one of its most quoted greetings, spreading through online edits, reaction videos and meme pages as shorthand for the film's awkward sincerity. It remains popular because it is instantly recognisable even to viewers who have never seen the full film.