- ===This is a list of fan theories. None of these have been confirmed in the game or by kouri, and they are simply ideas from the Ib fandom.===
Garry is Guertena
There are people who believe Garry is actually Guertena. There is strong evidence against this theory, the main piece being that Garry didn't know who Mary was. If Garry had painted Mary, he should have recognized her or vice versa. This theory is further disproved in the updated game, where Garry makes a few comments about the art, notably in the true gallery where he states that he doesn't really 'get' art and that artists must have a different way of seeing the world. Furthermore, according to a visitor in the gallery, Guertena is dead.
While the theory is far more plausible, there is no evidence proving that Garry is indeed Guertena's relative- if he was indeed the great painter's relative, Garry would have probably mentioned it. The only element that can tie the two together is found in popular lyrics to Mary's theme song, "Puppet" in which she asks why Gary looks like Guertena. However, the lyrics that mention this resemblance are fan made, therefore probably biased, and still allow for the existence of a coincidental similarity.
The Lady in Red is Guertena's wife/loverThis theory is actually mentioned in the game itself but it also says that Guertena denies this claim. It's possible that he could be lying and that the lady is a real person. Despite Guertena not painting real people, he has done so before, one example being The Juggler painting. Another clue that points towards this is, at the end of the Bonus Dungeon, the sculpture named "Tryst After Death", which shows a woman in red rising out of a picture frame embracing a skeleton.
Mary is symbolic for Guertena's unborn child
This theory does have some truth to it, as Mary sees Guertena as her father, and she refers to his other paintings as her brothers and sisters. But the true meaning is still unproven.
Garry is homeless
This theory is mainly based on Garry's ragged appearance. Though he does state that his coat is designed to be torn, it doesn't explain his messy hair. Also, when talking to him in the sketchbook world, he states that he had "a" macaroon at a café. Seeing how macaroons are rather small its odd that he would only have one, unless someone maybe gave it to him. And some also point out that the gallery seemed to be free, which is why he would come even though he "does not understand" art.
Guertena is in the gallery as you play the game
Several times in the game you get a text box that reads "There's no one there, but you feel a presence.". Lots of fans have thought that the presence is Guertena himself. A book also says something about immersing his spirit into his artwork.
Garry is mentally ill and about to snapPossibly one of the strangest theories, but there is some evidence. The first is Garry seeing dolls in the rabbit room which could be interpreted as him being schizophrenic - however, a text found in that same room suggest that it's actually Ib who is hallucinating and seeing rabbits to comfort herself amongst the creepy dolls. Others have pointed out that he seems to have mood swings, such as being terribly frightened of a mannequin head and then quickly getting angry at it despite his cowardly nature ; finally, a smaller amount of people think that he may have tendencies of pedophilia, hinting towards Ib, and that they may escalate - despite no trace of such tendencies existing anywhere in the game.
Carrie Careless and the Sketchbook
Some fans believe that Mary is the one who drew Carrie Careless and the Galette des Rois, as well as the Sketchbook. The reason for this is that both of these are drawn in a very child-like manner, and that Mary appears to be one of the few sentient beings in the painting's world. Furthermore, the Sketchbook is really Mary's own, secret world, and the only way out of the fake gallery, which would make sense because her dream is to leave it.
The "Real World" is actually the fabricated world
Seen in the Sketchbook, in the Gallery, is a drawing of Ib, Garry and Mary. Mary is given a yellow rose by a blue doll in this drawing. This might indicate that the "fabricated world" is actually the original, and that the "real world" is the fake one, that all people in the real world are drawn at any instance by denizens of the "fabricated world". However, an argument against this theory is that only Ib, her parents and Garry are encountered in painting or drawn form in the fabricated world, and that there is no sign of other drawn humans anywhere in the "fabricated world". Finally, both worlds claim that the other world is fake through the large painting seen at the start and end of the game.
Garry's sexuality has been debated by some, considering that he screams and is jumpy, has an interest in fashion, and not to mention, Ib has the option to ask him why he "talks like a lady". No other hint of Garry's supposed homosexuality exists, which makes this theory rather weak given habits and sexuality are not always related, and Garry could just be "feminine" without being attracted to males and/or identifying as more female. He precises that he talks the way he does "because it's better to be soft than rough", also suggesting that he primarily talks this way to children like Ib or Mary.
Guertena Died in a Fire
Or at least before he should have laid to rest.
The gallery responds violently when exposed to fire. Of course, this could just be because they can be destroyed by flames, but they can also be destroyed with many other things, such as being used as a bridge (like the ant painting), being stabbed with a palette knife, et caetera. They only seem to react so strongly to fire.
Moreover, the brown gallery has stairs leading to a new area just like any other area has, but then ends in the Sketchbook. The Sketchbook is obviously not drawn by Guertena, but the fact that those stairs exist implies he was planning on adding a new section to his gallery. Perhaps he was killed before he was able to.
A fire would definitely explain why only a handful of Guertena's paintings can be found in the real gallery when so many others exist.
Garry and Ib have a crush
Lot of fans think that these two characters are somewhat in love, because many scenes could be interpreted in a semi-romantic way. For example, when she faints and has a nightmare, Garry is worried about her ; afterwards, Garry uses his jacket as a blanket to cover Ib, and then feel worried yet again about how they were exposed to insanity-inducing material in the Fabricated World, despite being more prone to giving in to madness.
Another case is seen when Garry discovers that Mary is a painting and protects Ib from her and Ib hugs him, catching him off guard ; note that the same thing happens if Garry goes insane in the Doll Room and she brings him back to his senses.
In the fake sunlight, inside the Sketchbook, Garry will tell Ib about a macaroon he ate at a cafe, and he wants Ib to eat them with him. If the player gets the "Promise of Reunion" ending, he tells her that they will see each other again.
In others endings, when Garry goes crazy, Ib decides to stay with him in the Fabricated World ; likewise, it can happen that Ib lost her rose and Garry sacrificed himself by giving his to Mary. Finally, when Ib is about to jump in the painting to go back to the real Gallery but she sees a fake Garry, she confidently holds his hand and follows him.
Of course, all of these scenes could also simply suggest a sibling-like love, or a simple friendship.