If you're into this Japanese kawaii culture, this is the only place I know of in Pittsburgh that can help you get your fix. To find your way into this tiny basement shop, look for the sign near a mini-sidewalk-alleyway off Walnut and step down into it.
The first thing you'll realize is that you've never, ever seen so many Hello Kitty things in your life. Then you'll realize there's actually more around the corner. I had no idea what the rest of the licensing was, and most of it was in Japanese, but evidently there are other, similar fads to Hello Kitty with their own merchandise lines of odd cuteness that may or may not have a practical use.
This is a pretty popular shop, judging from the parade of shoppers filing through the cramped aisle, fawning over this and that cute and odd item. The cashier was very polite and ready to assist anyone who needed help. An interesting place to wander.