The sound comes from Mickey's Trailer, a Mickey Mouse cartoon released in 1938, in which Mickey, Donald and Goofy take a disastrous trip in a trailer pulled by a car. The passing train moment was lifted from that short and later shared online as a standalone vintage effect, where editors value it for its clear cartoon-era whistle and rail clatter. It remains in use because few modern recordings capture the same playful, theatrical style, making it a handy shortcut for retro travel scenes and classic animation tributes.