What does one buy a four-year-old girl for her birthday?!

I have a four-year-old sister (I'll be 23 soon) and her birthday was a few weeks ago, but because she lives 500 miles away, I waited 'til now to buy her present as I will see her next weekend.

But I still have no idea what to get! In the past I have 1) made her a blanket, 2) bought her a tee-shirt that says "My brother did it" (our brother is 21), 3) purchased her first Barbie doll, 4) got a Wizard of Oz dress-up set and 5) a snow globe with her name.

I'd like to stay away from all of the above, but she also has a TON of toys - especially various musical instruments. I rarely see my sister and want to get her something she'll love, but also not something that will break the bank.

Any help is greatly appreciated.

- M