One interesting plot twist could be that Steven discovers that he is the one who unknowingly created the time loop in the first place. Maybe his overuse of his powers in a particular situation disrupted the time - space continuum, leading to the loop.
Perhaps a plot twist where the gems within the time loop start to gain memories from different iterations of the loop. So they start to act differently each time the loop restarts, confusing Steven as he tries to figure out what's going on. For example, Pearl might suddenly remember a battle strategy from a previous loop that she didn't have access to before.
A really cool plot twist could be that the time loop is actually a form of protection created by an ancient and powerful being. This being saw a great danger coming towards Earth and the Steven Universe world, and the time loop was its way of giving Steven and the gems more time to prepare. So, while they think they are just stuck in a never - ending cycle, they are actually being safeguarded.
One plot twist could be that the pregnancy is not a normal biological one but is caused by some sort of magical or alien influence. Another could be that Steven tries to keep it a secret at first, but then it gets accidentally revealed in a really awkward or dangerous situation.
One interesting plot twist could be that a previously thought - to - be - evil gem actually has a noble reason for their actions. For example, a gem who was fighting against the Crystal Gems might be trying to protect a hidden colony of gems that would be in danger if the war ended a certain way.
A really interesting plot twist could be that Steven goes back in time and discovers that the Diamonds had different motives than he originally thought. Maybe they were being influenced by some other force in the past, and by going back, he uncovers this mystery. Also, he could find out that some of the things he thought were his friends' ideas were actually planted by an outside source long ago. This would completely change his understanding of the relationships and history in the Steven Universe world.
Steven himself is of course very important. He is usually the central character trying to break the time loop or understand its purpose. His unique powers and kind heart are often key elements in the story.
A possible plot twist could be that one of the Avengers, say Hulk, is actually a long - lost Gem. His transformation into the Hulk could be related to some dormant Gem power within him. This would completely change the way the other Avengers and the Crystal Gems view him.
One interesting plot twist could be that every time Harry repeats the day, a different character becomes aware of the time loop. For example, in one loop it's Hermione who figures it out and tries to help Harry break the loop in a very scientific way, using her vast knowledge. Another could be that Voldemort somehow gets a hint of the time loop and tries to use it to his advantage, like setting up different traps for Harry each time the loop restarts.
A really interesting plot twist in these fanfics can be when Spinel gets corrupted again, but this time Steven has to find a completely different way to heal her. It challenges his usual methods and tests their relationship. Another plot twist could be that Spinel starts to have dreams or visions about Steven's future, and she has to decide whether to tell him or keep it a secret. This can lead to a lot of internal conflict for Spinel and also affect her relationship with Steven in unexpected ways.
One idea could be that Lars and Steven go on a space adventure together. They might encounter new gem species and have to work together to solve problems. For example, they could find a planet where the gems are in a civil war, and Lars and Steven use their unique skills to bring peace.
A more emotional plot could be an OC who was once part of the Homeworld gems but defected. They have a lot of guilt and self - doubt because of their past actions. In the fanfiction, they try to make amends by helping the Crystal Gems. But they constantly fear that their old allies will come after them. This internal struggle and their journey of redemption could be a really interesting story.
In some fanfictions, a time loop might be caused by a powerful curse. The twist comes when Naruto discovers that the only way to break it is by making a huge sacrifice, like giving up his dream of becoming Hokage. This forces him to re - evaluate his priorities and makes for a very interesting read. It adds a new layer of depth to his character as he struggles with this difficult choice.