Rolling in stray litter outside of box

Hmmmm...lately Charm has been doing this strange thing. She'll lay right in the stray litter outside of the box. Then, to top it off, she'll roll around in it. Usually what I do is drag the vacuum cleaner out and get rid of it, but Charm digs in her litterbox with such gusto when she uses it - litter is constantly outside of the box - which isn't a huge deal as I vacuum on a regular basis. Just curious as to why she might be doing this odd behavior. She couldn't want to smell like kitty litter... Silly little girl.

Use a large plastic tub with high sides to keep the litter inside rather than outside. You can always cut a hole in the side of it for the cat to get in and out easily, if it is to tall for him to leap in and out of.