* Wondering why doesn't King Boo have his Jewel Crown in later games? Because Luigi sold it to buy his new mansion (even though the jewel is worth 1 COIN).
* Luigi doesn't get to the mansion until Mario's been captured. Player 1 lost a life, and now it's Player 2's turn.

* You go around sucking up ghosts for a little old man who turns them into paintings. While some of the ghosts, like Bogmire, are simply monstrous constructs, many of the ghosts are the ghosts of people, as in people who ''died''. Think about that: not only are you trapping the restless souls of the formerly living against their will, you're also ''flattening their very souls into paintings''! In other words, [[AlternativeCharacterInterpretation E. Gadd is a madman who uses]] ''[[AlternativeCharacterInterpretation human souls]]'' [[AlternativeCharacterInterpretation as decorations for his underground lair]]. To top it all off, one of the ghosts is a ''one-year-old child.''
** Or you could turn it around. All those paintings are haunted. While you're looking at them, they're looking back.
** Then again, this one year-old child was born a ghost. Plus, E. Gadd may be senile, but he isn't evil: the ghosts in ''Dark Moon'' who work for him are well-behaved and kind as long as the Dark Moon is around, so if the portrait ghosts actually did behave likewise, they'd be free to roam around as well.
* And then there's the heart quotes. Most of these are harmless little tidbits of speech that the ghost is keeping to themself. But then there's Sue Pea. It's a hint at how to beat her, but think. What if that quote was her last words?
* It gets worse. There's a bug in one part of the game that shows [[http://i86.photobucket.com/albums/k92/Aska49/luigismansion0000.jpg Luigi's shadow on a wall]], floating... or rather, [[DrivenToSuicide hanging]] in the air. [[UnfortunateImplications Dear God...]]
* To people who played ''VideoGame/PaperMario'', Luigi's cowardice seems weird. In that game, he was eager and adventurous. However, if you read his diary at one point, you can see he was already scared of ghosts. And the first game with Luigi's fearful personality? ''Luigi's Mansion'', where he has to travel through a haunted mansion. Luigi is ''traumatized''. [[ThereAreNoTherapists And nobody seems to be helping him]].
** [[CowardlyLion Yet somehow through all this traumatization]], [[CrowningMomentOfAwesome he took out an army of ghosts by himself]].
* There's those two ghost twin children who love to play hide and seek, nothing inherently wrong with that right? Well if you happen to find a diary in the study, reading an entry reveals that they both like to hide during the game, sometimes causing the game to go on for a very long time...oh dear.
** If you continue to read the diary, you'll realize that one of the twins is susceptible to cold. This is because planes weren't protected from the weather when they were first built by Orville and his brother.
* So WordOfGod is that Chauncey was actually born a ghost, so he isn't a dead baby after all!...Or maybe not. Being born a ghost could mean that's he's the result of a miscarriage.
** Or stillbirth.
** Or perhaps Lydia died while pregnant, killing the unborn Chauncey as well.
** Or Lydia and Neville just had another baby after they died and became ghosts, so that baby also became a ghost. Granted, they don't seem to have much in terms of lower halves, but they might have found a way.
* It's believed by some that King Boo's [[spoiler:Bowser "mech"]] isn't a mech at all, but rather [[spoiler:Bowser's corpse, with the Koopa King having been killed by Mario in a previous game]].
* If Luigi sprays ghosts with an elemental attack, they just fade away to nothing. [[spoiler:Note that most of them are made with paint...'''[[HiddenVillain and then you realize]] [[OverlordJr who]] [[TheReveal uses paint.]]''']]
** [[spoiler:Vincent Van Gore, the guy who created them. Bowser's involvement is nothing more than being the basis for King Boo's mech/suit in the final battle, and a mention beyond that from Clairvoya. Bowser Jr. isn't even implied to be part of the game.]]
* So, the portrait ghosts. It was already mentioned by someone else, they are real people being trapped in paintings against there will,you are the one doing it,etc. But have you ever gone to the gallery and noticed how they do not move inside the paintings like how Mario does? They just stand still, forever. So for the ghosts,it is like they are in sleep paralysis nonstop,unable to move or speak. And for anyone who has experienced sleep paralysis, you know how scary that is for just a few seconds or minutes. Now imagine that, but 24/7.
* Music/{{Brentalfloss}} points out that it's weird that Mario is unable to escape the painting, considering that he could go in and out of paintings in ''VideoGame/SuperMario64''. This could simply be explained by assuming that the painting Mario was trapped in works differently from the paintings in ''64'', but even if it ''did'' work the same, there's another explanation. In ''64'', Mario can't exit a painting unless he gets a Star, or he dies. As far as we know, not only are there no Stars in there, but there is nothing that could kill Mario. In other words, [[AndIMustScream he really was trapped]].

* During the blackout, you can enter the telephone room and receive phone calls from Toad and E. Gadd. How can the phones work without electricity?
** The same way a lightning bolt hitting the roof of the mansion and not an exposed power source can shut off electricity to the entire mansion and implicitly to E. Gadd's lab as well: [[MST3KMantra it's a video game.]]
** A lot of older phones didn't actually use electricity - they've been around as recently as the 2000s. I had one in my house growing up. I remember it being the only thing that still functioned during blackouts.
*** Correct. Older-style line phones are technically mechanical, not electronic, merely turning line noise into audible noise by passing electric signals through magnets. As long as the line is intact, they require no electricity.
** Similarly many land line phones actually run on a separate circuit system from main power which is why the older ones don't need to be plugged in to a wall outlet just a telephone jack. So generally speaking an older style land line, even up to the 1990's in some places like the continental United States, would still operate in a black out so long as phone lines remained intact.