Your exploration beyond the first passage has stirred the very soul of One-Eyed Willie himself! As you get closer to his final resting place, this apparition will attack you in an effort to throw you off the trail of his precious treasure. Don't let the sight of him deter you from your mission.
Stage 3 is the largest stage that you will explore. Steam valves release scorching hot blasts of steam when the pressure builds up, but a raincoat can protect you from them. The first three sections are required, but the final part, part D is entirely optional. You begin the stage above and slightly to the right of skull mouth A. Since you're so close to it, you might as well pass through it to reach part B. Bomb the door to the upper left. Then drop down from that ledge and travel far to the right to open the other door. Return to skull mouth A and pass through it to part A.
From skull mouth A, climb up both nearby ladders, and jump over the gap in the pipe to find another ladder that brings you to the top of part A. Open the door that's above you when you arrive. Then proceed to the right and over to skull mouth B. Pass through the mouth to reach part C. In part C, run to the left to reach the ladder. Continue running to the left and climb into the small chamber to look for an important protective item. After that, run to the right side of part C to find and open two more skull doors. Then return to skull mouth B and pass through it to get back to the top of part A.
Back in part A, climb down the ladder to the lower floor, and climb down the closest ladder to reach the middle level of part A. Climb all the way down to reach the skull door at the bottom. Once you open it, climb back up the nearby ladder and proceed all the way to the right, where you will find a ladder that takes you to the lowest section of part A. Open the skull door that you pass while climbing down the very long ladder.
You may or may not have all of the necessary items for exiting the stage, depending on the contents of the very last door at the far left of the lowest level. How you proceed next is up to you. If you manage to find the hidden Jump Shoes, you may wish to explore what lies below ladder C. If you take ladder C without the Jump Shoes, you will be incapable of reaching the high ledge to the left of the ladder. If you are wearing the Jump Shoes, you can clear the ledge easily and proceed to the ladder on the left. If you climb down the ladder, be aware that this is a one way trip. You will not be permitted to return, and you will bypass Stage 4 entirely, warping directly to Stage 5. You will, however, discover the fourth hidden Goonie in a special location so that you don't miss the chance to see the ending sequence. Don't forget to bring a bomb before taking this shortcut. If you do not wish to warp, exit the stage normally through the lower left corner of part A.
Diamonds are widely spread apart in this level, but still worth searching for since you can incur a lot of damage with One-Eyed Willie's ghost floating about. Among the hidden items in this stage, one is valuable throughout the rest of the game, one is only useful in a small portion of this stage, and one guest appearance grants you bonus points
This helmet does what any well made football helmet should do: protect your head from falling stalactites. Unfortunately, it won't do you a lot of good against the giant falling boulders found in Stage 4, but it is still useful being able to run underneath the pointy rocks without fear.
You might think that once Mikey finds these he would wear them all the time. Unfortunately, the kinks haven't been worked out of them, so they're only really useful in one section of the game, part D of Stage 3. If you climb down the long ladder, you will automatically don the Jump Shoes and make the tremendous leap required to reach the top of the ledge to the left. Following the path will lead you to a warp that bypasses the fourth stage and takes you directly to the fifth. You don't even need to collect all of the keys in Stage 3 to do this (although you should at least try to find the capture Goonie).
A guest appearance by Konami's own Twinbee will fly along the screen from left to right. If you make it appear as you are running along the pipe where he can be revealed, he will meet you at just the right time when you jump to clear the gap in the pipe. Collect him for 5000 points.