The line comes from American Psycho, the 2000 film directed by Mary Harron and based on Bret Easton Ellis's 1991 novel, where Christian Bale plays Manhattan banker and serial killer Patrick Bateman. When colleagues press him, Bateman calmly claims he has to return some videotapes, a mundane errand that clashes with his dark double life. The quote took off online as the perfect deadpan exit excuse, quoted in forums, memes and video captions whenever someone wants to leave without explaining themselves. Its polite absurdity keeps it endlessly reusable.