I used to do this to my girls' jeans after school let out. Great way to boost the summer wardrobe for next to nothing! Transform an old pair of jeans into adorable summer shorts using bias tape. Instructions on the site.
I'm not that into pandas, and neither is MiniDork. But oh man, the animals you could adapt this to! My kidlet would love a kitten-sleeve or puppy-sleeve shirt! Flocked Heat Transfer Panda Sleeve by Jennifer of Parrishplatz