"Un forastero" comes from Resident Evil 4, the 2005 survival horror game from Capcom. The line is spoken by one of the villagers in the early village encounter, where enemies alert each other after spotting Leon. It became memorable because Resident Evil 4 was hugely influential and its enemy dialogue stuck with players for years. Online, the clip spread through game compilations, memes and reaction edits, and it is still used as a quick way to signal that an outsider has been detected.