Little Big Adventure 2: Twinsen's Odyssey

While in the sewers a little jumping on the floating logs will
reveal a four leaf clover. If you keep going around the circle on
the logs you will also come to a box and a key under the walkway.
The key opens the door in the sewer wall. Now *every* time you go
in the room and then come out two things happen, the box and key
reset themselves in the sewer, and the four leaf clover resets!
Used this to fill all your clover boxes.