A common and really engaging plot point is the idea of a common enemy. In some fanfictions, a super - powerful being emerges that is a threat to both Goku and Saitama's worlds. This forces them to team up, and seeing how they combine their powers and strategies, with Goku's strategic combat thinking and Saitama's simple but effective punching, is really exciting.
One interesting plot point is the clash of power systems. Goku's ki - based attacks and transformations like Super Saiyan contrast sharply with Saitama's pure physical strength. For example, in some fanfictions, when they first meet, there's a sense of mutual curiosity about each other's power sources.
One interesting storyline could be that Goku, being the ever - eager fighter, challenges Saitama not knowing the true extent of his power. Saitama, on the other hand, is just looking for a normal grocery shopping day. The clash of their personalities, Goku's excitement and Saitama's nonchalance, could lead to a very comical start. Then as the fight progresses, they both start to respect each other's power in different ways.
Well, often a plot point is the culture shock. For example, Saitama being in RWBY's world and not understanding things like Dust or the Grimm. It's funny to see how he just approaches everything with his 'one - punch' mindset. Another is the power - level differences. RWBY characters have their own set of powers which are quite different from Saitama's extreme strength, and seeing how they interact in battles or training is really engaging.
One interesting plot point is when Goku tries to learn magic. It's hilarious to imagine him struggling with a simple levitation spell when he can usually just use his Ki to fly. Another is when Harry Potter tries to learn martial arts from Goku. It's a great clash of two different power - building systems.
One possible plot could be that a new and extremely powerful villain emerges who is not impressed by Saitama's one - punch ability at first. This villain manipulates the rules of the tournament to his advantage, creating unfair match - ups for the heroes. The heroes then have to find a way to overcome these obstacles while also dealing with their own rivalries and personal growth. For example, Genos could be paired against a much stronger opponent early on, and in the process of trying to defeat this foe, he discovers a new power - up within himself.
One common plot twist could be that the reincarnated character has some unique power that even Saitama is interested in. For example, they might have a power that can nullify Saitama's strength temporarily. Another plot twist could be that the character is reincarnated as a monster but still retains their human consciousness and tries to find a way to co - exist with humans. Also, a plot twist might be that the reincarnated character discovers a hidden conspiracy in the One Punch Man world that even the heroes don't know about, like a secret organization controlling the appearance of monsters.
One interesting concept is the power level comparison. Saitama's seemingly limitless strength compared to the Force - using abilities in Star Wars. It makes for an exciting exploration of different power systems.
Well, a really interesting crossover is when the power systems of both universes collide. For example, when Fairy Tail mages try to understand Saitama's power which is seemingly limitless. It creates a lot of mystery and awe.
One plot could be Tornado having to team up with a new, unexpected hero to face a powerful villain that even she has trouble with. This would show a different side of her as she has to work with someone she might not initially get along with.
One idea could be that Saitama from One Punch Man somehow ends up in the world of Overlord. He might be mistaken for a powerful player at first. Since he's so strong, he could easily defeat many of the powerful monsters in the Overlord world, which would cause a stir among the various guilds and NPCs. Another plot could involve the characters from Overlord trying to understand Saitama's power, which is beyond their comprehension as it's not based on magic or typical RPG stats.
One idea could be that Saitama somehow gets transported to the DC universe. He might initially be confused by all the superpowered beings there. Maybe he enters a hero - villain battle in Gotham and just one - punches all the villains, which both amazes and confounds the local heroes like Batman. They start to investigate this strange, bald - headed, extremely powerful man.