if you want a quick star, all you have to do is this. you know the first painting you go through?. there is a big chainchomp chained to a wooden stump, ground pound the stump a few times, and eventually the stump will dissapear, releasing the chainchomp, and the chainchomp will also clear the bars preventing you from getting the star that was behind the bars.
here is a youtube video which shows exactly what im saying