The line comes from Doctor Who series 7 opener Asylum of the Daleks, first broadcast in 2012, with Matt Smith as the Eleventh Doctor speaking to Oswin Oswald, played by Jenna Coleman. In context it is a tense, practical order during their escape from the Dalek asylum, not a joke. Clipped out of context, the blunt phrasing took on a second life on meme pages and soundboards as a suggestive punchline. Its lasting appeal comes from that Doctor Who contrast, a normally family-friendly hero sounding unexpectedly cheeky.