Hey Guys & Gals!
I have a 100% Achievement Guide for this game if you prefer a visual!
From the courtyard, head down north one screen and you will see our donkey boy once again just chilling.
If you have looked around in chests ETC you should have an apple in your inventory, so first put three candles down around the donkey (VERY important for another achievement related to donkey boy later on in the game).
Once that is done, simply feed donkey boy an apple, and he turns into a unicorn and craps gold for some reason which you can pick up
.
Excellent!
Go to 24:50 in the video to see where and how this is done.
Hope this helps!