Big Iron is a western ballad by Marty Robbins, and its opening verse introduces a stranger riding into Agua Fria. The song gained a second life online when creators paired its calm storytelling with Fallout: New Vegas footage and other western-themed edits, turning the first line into a shorthand for a confident arrival. Because the tune is instantly recognisable and the lyric sets a scene in seconds, it still works as a quick setup for showdowns, entrances and deadpan jokes.