Songs from Beyond the Grave
If let a kid watch YouTube for too long, they might be able to pick up songs from different languages. They can sing happy birthday in Korean, Indonesian, and Polish, but they might have trouble stringing two English words together—just something for parents to think about.
But when your kid starts singing an old Polish song, even though you guys don’t speak Polish at home, and it’s a song that your grandmother used to sing a long, long time ago, then maybe you might need a house visit from a priest or something. At the very least, you should determine whether or not it’s actually the spirit of your loving grandmother.