I agree with Michael. It would be nice to handle the issue of same-named costumes per sprite generically whenever we add a costume to a wardrobe. If you didn't run into any performance issues I'd much more prefer you used a function on the wardrobe every time to check for name conflicts than to cache every name. As a general rule caching can be very tricky because it can become inconsistent, and you usually end up creating awfully complex mechanisms to ensure and handle consistency. So, functions are a great way to check for things :-)