Ruby would be an obvious choice. Since they are both friends in the RWBY series, a crossover could explore a deeper bond between them. Maybe they go on a special mission together that takes them to a new and dangerous part of Remnant. Another good character could be Weiss. Their different personalities and fighting styles would create interesting interactions. Weiss' ice powers combined with Penny's technological abilities could make for some cool combat scenes.
Well, a great concept for 'rwby penny crossover fanfiction' is Penny getting a power upgrade from an unexpected source. Maybe she encounters an ancient relic that gives her new abilities. She could then use these to help the RWBY team in a more significant way. For example, she might be able to communicate with Grimm and understand their motives, which could change the whole dynamic of how the RWBY gang approaches fighting them.
Of course, there's also the possibility of Penny interacting with characters like Professor Ozpin. Ozpin is a knowledgeable figure in the RWBY world and could provide Penny with advice on her new existence as a real girl. And then there are the villains. If the fanfic has a plot where Penny's new state is a target or a threat to the villains, they would also interact with her in some way, like trying to capture or manipulate her.
Well, this kind of fanfiction often explores unique concepts. It might involve the character from RWBY being reborn as Penny. Maybe it'll show how the character adapts to Penny's life, her abilities and relationships. It could also bring in new storylines that are different from the original RWBY plot.
Superman from the DC universe. Superman stands for truth, justice, and the American way, but his methods are often more lenient compared to Akainu. The two could have a philosophical debate about justice while also having to fight a common enemy.
One plotline could be that Penny is hacked by an enemy and turned into a brainwasher to manipulate her friends in RWBY. This would create a lot of internal conflict as the team tries to figure out what has happened to her.
Ruby could also be a protagonist in this crossover. Imagine if she somehow gains gamer - like abilities. She would be able to use her scythe skills in new and exciting ways, like having combo attacks that are based on gaming mechanics. She could also level up her speed and strength in a more quantifiable way, which would make her even more formidable against the Grimm and other foes.
In the 'rwby penny fanfiction' world, 'Penny's Redemption Arc' is quite popular. It delves into Penny's character more deeply, exploring her past mistakes and how she overcomes them. It's a great read for those who want to understand Penny on a more profound level. There's also 'Penny's Friendship Chronicles' which focuses on Penny's relationships with the other characters in RWBY, showing her growth through these connections.
A character like Dracula could be an interesting crossover. His immortality and dark powers would contrast with Aruto's nature. Also, Merlin from the Arthurian legends would be a great choice. His magic and immortality could lead to some really cool interactions with Aruto.
Definitely Superman. Superman's super strength and Gohan's Saiyan power would make for an interesting combination. They could have a friendly sparring match to test their limits. Another good character could be Ichigo from Bleach. Ichigo's sword - fighting skills combined with Gohan's martial arts and ki blasts would create some epic battle scenes.