Changelings are a mythological concept found in European folklore, particularly in Celtic, Germanic, and Scandinavian traditions. A changeling is believed to be a fairy, elf, or other supernatural being that is swapped with a human child. According to the legend, fairies or other mystical creatures would secretly take a healthy human baby and leave behind a changeling—a creature that looks like a human child but is sickly, different in temperament, or even malicious.