Here's mine (which is genuinely called a "buttocks basket") ...
Although my buttocks are not especially well-formed, I think you can see where it gets its name :o)
We used two different kinds of willow. They were both quite green and they were not stripped of the bark, so there was a lot of variation in the colours, which I loved.
In this one, you can see why my DH said it reminded him of the knickers we used to put over babies' nappies!
This is definitely something I would love to do more of when I have time. Three of my friends made beautiful berry baskets and another made a gorgeous lantern. I also love the idea of creating living willow structures for the garden - another one to add to my list for when I retire :o)