Wario Land-Super Mario Land 3 "Course no. 18"

To find this secret goal, make your way through the first screen
all the way, and enter the door at the otherside. On the second
screen, you will see a lone coin to the right. Get underneath it
and jump up to reveal a hidden block. Jump on that, then jump up
again and you will be in the ceiling. Now head right and you will
drop down to a secret room. Get the coins and enter through the
door. On this third screen, head right to the otherside (there
will be a Boomerang Duck along the way), and you will see the
secret goal door. Open it up and enter it and you will have
completed this secret goal. On the Level Map, a new path will
appear leading to Course 18.