A few days ago I
linked to a brilliant fanvid showing all the times that the phrase "What are you doing here?" or variations thereof is used in Doctor Who - including the very first words spoken in the role by William Hartnell in the first episode.
Actually it has a long and glorious literary history. In Beowulf, back in the 7th century, the very first lines of direct speech in the poem are these words of Hrothgar's herald greeting Beowulf's party:
Hwæt syndon gē searohæbbendra,
byrnum werede, þē þus brontne
cēol ofer lagustrǣte lǣdan cwōmon,
hider ofer holmas?
which Seamus Heaney renders:
What kind of men are you who arrive
rigged out for combat in coats of mail
sailing here over the sea-lanes
in your steep-hulled boat?
or in summary
What are you doing here?
(Lines 238-241, if you want to check.)