The effect comes from Canine Caddy, a Mickey Mouse cartoon released on May 30, 1941, featuring Mickey and Pluto on a golf course. Its scratching, sniffing and razz noises are classic hand timed animation foley, later catalogued in studio sound libraries including Hollywood Edge collections. As those libraries moved into digital editing, the clip survived as a compact go to for cartoon dogs. Editors still reach for it because a few frantic seconds instantly signal searching, digging or mischief without needing a real animal recording or any spoken joke at all.