Apparently, Starting from 0x010EEE1C, there's a nice amount of unused sprites on Super Princess Peach.
The Koopa Kids!
Unfortunately, only one of them is ripped. With pain.
After opening the ROM on a tile viewer and creating a custom palette, I was ready to go.
With a 3.5 hour Ripping process involving 3 liters of Coca Cola, I finally had managed to get them.
There are also Other Koopa Kids, Ludwig, Wendy, etc.. But I don't feel like ripping them now..
Please enjoy it. I've also ripped Peach But It's somewhere in the depths of my photobucket.
It is believed that the Koopa Kids are accessible only through a process which involves Legend of Stafi. In case you didn't know, if you have Legend of Stafi on your GBA slot while playing SPP, you'll eventually see Stafi himself. This has not been proven yet, but is a popular belief.