In some fanfictions, a character who was supposed to be a minor villain in the original 'Bleach' series becomes a key ally during the 'watching' part. This sudden change in allegiance is a really cool plot twist.
A really unexpected plot twist can be when the characters from the 'Bleach' series find out that the 'watching' is actually a test set up by a higher power. And the outcome of this test could determine the fate of their entire world. This adds a high - stakes element to the fanfiction and makes for a very engaging read.
One possible plot twist is that the hogyoku from Bleach somehow ends up in the hands of a character in Highschool DxD. This could lead to a character attempting to use it for their own gain, perhaps to gain ultimate power over both the devils and the angels. Another interesting plot twist is that a character from Highschool DxD gets reincarnated as a Soul Reaper in Bleach. They would have to learn the ways of the Soul Reapers while still retaining some of their previous abilities and memories. This could create some really interesting character development. A third plot twist could be that the balance between the three factions in Highschool DxD (devils, angels, and fallen angels) is disrupted by the arrival of Hollows from Bleach. The factions would have to figure out how to deal with this new threat, and it could lead to some unexpected alliances.
One interesting plot twist could be a character from Bleach accidentally getting sent to Yokai Academy. Maybe Ichigo ends up there and is mistaken for a new yokai student. His reiatsu could be misinterpreted as some kind of strange yokai power, leading to all sorts of chaos as he tries to figure out how to get back home while also dealing with the unique challenges of the academy.
Perhaps a plot twist where the Geass power is revealed to be related to the Quincy powers in Bleach. This could mean that there is a deeper connection between the two universes. If Lelouch was part Quincy all along, it would change his character arc. He could then have access to Quincy abilities like Blut Vene and Blut Arterie, which would give him an edge in combat against both Britannian forces and any potential threats from the Bleach universe.
One interesting plot twist could be that a Shiba character from the past travels to the future and discovers that their clan has a completely different role or status. For example, they might find that the Shiba clan, which was once powerful, is now in a state of decline. Another twist could be related to a time - travel - induced change in the relationship between the Shiba and other important clans in the Bleach universe. Maybe a long - standing feud is suddenly resolved because of an event that occurred during the time travel. A third possibility is that a Shiba character's time travel accidentally alters the course of a major battle in the Bleach storyline, leading to unforeseen consequences for all the characters involved.
One interesting plot twist could be the sharing of powers. For example, Naruto's chakra abilities might combine with a Bleach character's spiritual power in an unexpected way. Maybe Naruto could gain the ability to use a zanpakuto-like weapon with his chakra, which would be a huge change in the battle dynamics. Another plot twist could be a character from Bleach getting access to Naruto's sage mode knowledge, leading to a new form that combines the two universes' powers. And of course, there could be a plot twist where the villains from both universes team up, forcing the heroes to put aside their differences and come up with a new strategy to fight against them.
Well, perhaps a major plot twist could be that the CCG (Commission of Counter Ghoul), which is supposed to be against ghouls, has been secretly working with some ghouls for their own ulterior motives. This would be a huge shock as it goes against everything they are known for. Also, there could be a twist where a ghoul's kagune (their weapon - like organ) mutates in a way that gives them an unexpected advantage or disadvantage.
In some fanfictions, like 'The Unlikely Alliance', the plot twist is that the Hulk is actually being controlled by an unknown villain who wants to use him to take down Batman. Batman has to figure out not only how to stop the Hulk but also who is behind it all.
One interesting plot twist could be when a Splatoon character suddenly gains Naruto - like powers. Imagine an Inkling being able to use the Rasengan. It completely changes the dynamic of the story.
A really interesting plot twist is when the villain in the fanfiction turns out to be a character who was initially thought to be an ally. For example, in a story where the Vikings and Arendelle are working together, a seemingly helpful Arendelle noble is actually in league with a dragon - hunting group from httyd. It throws everyone into chaos and makes for a great read.
A really interesting plot twist can be when the characters from Undertale end up in the Naruto world and they have to adapt to the ninja way. For example, Sans using his shortcuts in the middle of a ninja battle, which throws everyone off guard. It's unexpected and adds a whole new level of humor and chaos to the story.