I second this. I happened to be in Middleton, WI on National Mustard Day (which is apparently a real "holiday"). They had a bunch of mustard themed midway games set up and a band like a little festival. The museum itself was pretty neat as well. The gift shop is why I recommend people stop by if the happen to be in that part of Wisconsin. They have over 500 types of mustards you can buy[1], and have a free samples counter that lets you try probably around 10. Some of them are extremely unique. I think the oddest one I tried was the peach champagne mustard because for whatever reason I didn't expect it to be so sweet. I still use the classic beer mustard I bought from there.
[1] https://store.mustardmuseum.com/category/buy-mustards