the door that's locked
The small key in Astro Knights Island is for Mordred's secret hideout. When you come to that wind mill area, move the hay bales apart and use the key on that.
You do not get or use a bucket on Astro Knights Island.
There is no treasure chest on Astro Knights Island.
There are no bird eggs in astro knights island.
its on the island
How do you talk to the girl in the hay loft at astro knights island?
The attic of the windmill doesn't have a key, only an ingenious secret. (see the releated question)
On every island you have to be the one to save whatever needs saving. That includes the kingdom in Astro Knights Island.
Go to the hay bales and push them apart. The key opens the hatch to Mordred's underground laboratory.
Once you have built a new spaceship on Astro Knights Island, it will park on top of the castle whenever you leave the island.
it is in the left
Astro Knights