Released in 1981 by Australian band Men at Work, Who Can It Be Now was written by singer Colin Hay and featured on the album Business as Usual. Greg Ham's saxophone part helped it reach number one in the United States in 1982. Hay wrote it while living in an apartment where unexpected visitors and bill collectors often knocked. Decades later the short hook resurfaced online as a reaction sound for unwanted callers and surprise arrivals, because its question sums up that wary feeling instantly.