What plant does this seed come from? I remember it being a low growing, sprawling weed that produced a ton of these little seeds that easily stick to clothes. In Northern California.
I'm pretty sure it's a burclover (Medicago sp.). Hard to tell from the picture, but if the seeds (well, technically, the fruit -- the seeds inside look like this) have a very obvious spiral growth pattern at the base, and it's a clover with small yellow flowers, it's definitely a burclover.
I don't know that much about California's flora, but one very widespread Medicago species there is M. polymorpha, an invasive species native to the Mediterranean which certainly fits the description of "low growing" and "sprawling" and "weed" and "a ton of these little seeds that easily stick to clothes".