This map shows the areas where Castles are present.
The Castle is an enemyhead in Stick Ranger. Its first appearance was in Snowfield 2. So far, there are 11 enemies with the Castle head in Stick Ranger. The combined population of enemies with this head in Stick Ranger thus far is 467.
There is a similar head also called the Castle head on the Fan-Ball Wiki. This may be a signal that ha55ii has seen the wiki, or one of his developers had. Although nobody can be sure, since this may just be a coincidence. (View picture to the right for comparison.)