This is something I wanted to try as a kid, but never got to do. So when Builder Boy started telling me how to do it, based on what he learned watching the Bill Nye the Science Guy episode on farming, and asked me if we could do it, I said "of course!" Principal Daddy picked up some heavy whipping cream at the store and a few days later we started shaking. I'm not sure if we were suppose to get heavy whipping cream, but Daddy said there wasn't anything labeled just "heavy cream," so this is what we ended up using. I put a small amount in a plastic container with a screw lid because I didn't want to risk the kids dropping a glass jar like they showed on the show, and I thought plastic would make it less heavy and make it longer before we got too tired.
10 minutes later and no butter. "We need something to make this go faster." What do you think we need? "A factory."
We don't have a factory. I once made butter by accidentally over beating whipping cream, so I suggested using the beaters. "Yes, the beaters will work because the beaters won't get tired!"
A few minutes later and we finally had something that was solid enough that we declared it "homemade butter." Technically, since we didn't separate the milk fat from the liquid, I don't think it really counts. But that didn't matter to the boys. They just wanted to see milk turn into butter. They were perfectly happy with the product, and it's taste.
Afterwards I told them about churns, and what people had to do before they had factories and electricity in homes. I used the Wikipedia article and a youtube video of a family using an old fashioned churn.