In my elementary school in Wisconsin, we had a Pioneer Day in fourth grade where everyone dresses and acts like a pioneer for a day. We would do Johnny Appleseed activities, sing ring around the rosie, had field trips to Cave of the Mounds and Little Norway. These all seemed "normal," since my older siblings had all done them, so it was no surprise to me when these events or activities came up in the elementary years. Through Erik's blog, I learn about things that could be considered "normal" for some Spanish children.
The lyrics (and his English translation of them) are definitely worth a look on his post. In fact it was the lyrics of this song (sung by children) that really caught my eye and got me thinking: How did this tradition get started? Do the kids understand what they're singing about? Do their parents? Or is it just so commonly heard around this time of year that it's built into the culture, no one questions it?
The wikipedia article linked to above helps answer some of those questions, about the history of the song and tradition.
Can you think of any American celebrations, customs, or songs that would seem extra strange to a foreigner?