(From Super Mario Wiki) The PAL Hidden Mansion is mirrored from left to right when compared to the Normal Mansion. The NTSC version keeps the layout the same. There are more normal ghosts around the mansion. Bosses are harder, having different attacks (Chauncey's rocking horses, for example, are much bigger, and swerve left to right instead of going straight). A major change in the Boolossus battle is that the player rides around on the vacuum cleaner while trying to pop Boolossus, making movement more slippery. Rooms are much darker in the PAL version; this, however, is only as dark as in the NTSC version of both mansions, the normal PAL mansion being lighter. Most Boos have more HP in the PAL version, although some have less. Fewer hearts. Locations that always had hearts in the Normal Mansion no longer have them. Hearts that heal 50 HP no longer exist. Speedy Spirits and Gold Mice always give up a Blue Diamond when caught, adding an extra 50,000,000G to the maximum possible amount of money. Possibly (not confirmed) up to five times more power for the Poltergust in the PAL version. 45 rather than 40 Boos are required to fight the final boss. Boos are, in general, more agile.
(this sig was blown up by Zero) People in the pit:22