From the Super Mario Wiki, the Mario encyclopedia
According to Professor E. Gadd, the first twenty one portrait ghosts and Boolossus (No. 22) were released from their paintings by Boos under the command of King Boo. Luigi had to vacuum up all of the portrait ghosts (except for a few "optional ghosts" like Mr. Luggs) using the Poltergust 3000. Captured portrait ghosts would be returned to their paintings via the Ghost Portrificationizer. The frame and the style of the portraits would change depending on how many pearls Luigi acquired during the battle with the ghosts.
Black and white pictures can be found in many rooms of the mansion. These pictures look similar to each ghost that inhabits the room they are in, suggesting these pictures may be depicting these ghosts when they were alive. Pictures resembling Neville, Lydia, Nana, Vincent Van Gore, Spooky, Chauncey, Mr. Whirlinda, Slim Bankshot, Henry and Orville, and Sue Pea can be seen in the Parlor, Study, Nursery, Ball Room, Billiards Room, Twins' Room, and Guest Room.
All of the portraits were given new designs in the Nintendo 3DS remake.
List of Portait ghosts
Note: Although Luigi first meets Madame Clairvoya in Area Two, he captures her after he begins Area Three.
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