Secret Room in Stage 1
In the very first stage of this game, there is a hidden room. In the first stage, you must climb ropes to get through the level. The second to last rope, on the right-hand side of the screen, leads to a platform with a tree stump and 2 graves with crosses visible. If you climb up this rope above where it appears to end at a brick wall, you will climb into a hidden room with four power-ups.
Submitted by Bruce Baier (baierb@hotmail.com)

Secret Room in Stage 2
In the second part of the stage, where you have to choose between ropes, go right, then go left. You should be in a room where you go down stairs, and giant eyeballs are speeding toward you. Kill an eyeball while it's on the middle step. Once done, a hole will open up. Climb down it for power-ups.
Submitted by Alex Williams (rickw@idt.net)

Secret Room in Stage 3
At the end of stage three, you climb a long rope on the left of the screen with a thick wall to the right of you, this is right before the sub-boss at the end of the level. When you are about half way up that long rope you should be able to jump into the wall and walk to the right towards a variety of power-ups.