The image from 'Wings of Desire' below reminds me of an episode of Columbo (the connection being Peter Falk). Colombo arrives at a soup-kitchen in a run-down part of town while investigating a case, and looking as dishevelled as ever. The woman in charge looks him up and down and says 'Oh you poor man, come in and we'll fix you up with something to eat'. Eventually Columbo manages to explain to her that he is, in fact, a police officer. 'I see', she whispers knowingly, 'you're working undercover!'