Feliz cuypleaños is a popular Spanish wordplay greeting in Peru and other Andean regions, where cuy means guinea pig, an animal with deep cultural and culinary importance. By changing one letter of cumpleaños, the phrase turns a standard birthday wish into an affectionate joke for friends and family. Online, the sung version circulates as a short shareable audio for birthdays, passed around in chats and edited into celebration videos. Its appeal lasts because the pun is instantly understood by Spanish speakers, while the singing makes it feel warmer and funnier than a plain text message.