Perhaps a plot twist could be that Harry's mother was in on the secret all along. This would completely change the way we view her relationship with Snape in the original story. It could also lead to revelations about her motives and actions throughout Harry's life.
Some students might be shocked at first. They've always known Snape as this rather complex and often unfriendly character towards Harry in the original story. So, the idea of him being Harry's dad completely flips their perception.
One possible plot twist could be that Snape has a hidden agenda all along. Maybe he's been using Harry as a pawn in a bigger scheme related to the wizarding world's power struggle. Another could be that Harry discovers a long - lost family connection to Snape that changes their dynamic completely.
One possible plot twist could be that Snape blackmails Harry into joining a secret magical society at Hogwarts that Snape is leading. This society could be dedicated to protecting a powerful but dangerous magical artifact. Harry initially resists but realizes the importance of the cause as the story progresses.
One possible reason could be that in this fan fiction, Harry has developed a deep respect and a father - like bond with Snape over time. Maybe Snape has been secretly mentoring Harry in potions and has shown him kindness and understanding that Harry has never really received from his own father figure. This has led Harry to subconsciously view Snape as a father figure and the moment in potions class is just when this feeling overflows and he blurts out 'dad'.
A possible plot twist could be that Snape is actually the one who arranged for Harry to be sent to Azkaban, but for a noble reason. Maybe he knew that Harry was in danger from a more powerful dark force and Azkaban was the only place that could keep him safe temporarily. Another twist could be that the real culprit behind the crime Harry is accused of is someone very close to Snape, and Snape has to choose between protecting that person and helping Harry. It could also be that Snape discovers that Harry has a hidden power while in Azkaban that could change the fate of the wizarding world, and he now has to keep Harry alive at all costs.
One possible plot twist could be that Snape discovers some hidden magic in Harry that he didn't expect. Maybe a power that's related to the Potters but also has a connection to Snape's own family. Another twist could be that the other Potter family members don't approve of Snape adopting Harry, leading to a family feud within the wizarding world. And perhaps, there could be a dark force that tries to use Snape's new relationship with Harry against them.
One interesting plot could be how Snape reveals the truth to Harry. It could be a very emotional and tense moment. Maybe Snape has been hiding it for years out of fear or some other reason, and when he finally tells Harry, it completely changes Harry's perception of himself and his past.
A really interesting plot twist could be that after getting pregnant, Lily loses her memory. So Snape has to deal with not only the fact that he's going to be a father but also that Lily doesn't remember their relationship. And then James steps in to help, thinking the baby is his. This would create a very strange love triangle situation. Also, what if the baby Harry has some sort of special power from the start that no one expected, which could be a major plot twist.
One possible plot twist could be that the kidnapper is actually someone close to Jacksepticeye, like a friend or a crew member with a hidden agenda. Another could be that Jacksepticeye has a secret ability or knowledge that he uses to turn the tables on the kidnapper.
Snape might be initially shocked. His face could turn pale and his eyes widen in disbelief. But then, a small glimmer of something like pride or warmth might flash across his face for a split second before he quickly composes himself and snaps at Harry to focus on the potion.