You can unlock a Cheat called 'Comedy Shoes!' then enable it in the secrets menu!
Go to the Mordant St. NY. Follow the paths until reaching a room with a lever. Pull the lever and the lights will turn on. Enter the elevator and go up. Go find the door, then look for a brown patch on the floor. Jump as far as possible, then jump again. If you fall through, use the bear to warp there and try again you need the floor that falls for the second jump.
Go to Deadside: Marrow Gates. At the beginning of the level, go to the left and climb up the blood waterfall. Open up the Shadow level 10 Coffin Gate (120 Dark Souls). Along with a "Thank You", you will be able to see pictures drawn during the game's development.
Not in the N64 version.