Chaotic_Chewtoy's Secret Quest map and X The Legend's hat list is mostly right, except that there are no hats to be found in room 15. Snail Face is right, the Pink Yoshi hat is in room 22, while the Chomp hat is from room 7, second time round, after ? Block and before Barbera the Bat.
Also, the map refers to fourth and fifth runs. This seems to have caused some confusion; really, it only needs to mention third runs as three is the maximum number of hats a room has in it. It doesn't matter what order you do most of the rooms, or which run you're doing, what matters is how many times you have completed a room. In fact, EpicLuigi calculated that it will take a minimum of 9 runs to get all the hats. If the above information is incorrect then this is true, but as the Pink Yoshi Hat is in room 22 you do have to take the bottom path a second time, bringing the minimum total to 10 runs.
Same for the silver key. You can visit room 19 as many times as you like, but if you havn't taken the top-most path, you won't get it. Also, if you took the bottom unlocked path first, then the top, you'll get the silver key in room 25. You don't need to do the middle path.
One final observation, just if anyone's interested, is that, in PAL, the Hatchet Hat is named the Horror Hat. Censorship. Awesome.
