Well, it could be that there's a portal that opens up between the MyStreet universe and the FNAF universe. Characters from both sides accidentally cross over. The MyStreet characters are shocked by the horror - filled FNAF world and try to find a way back while also helping the trapped souls in the FNAF world. And the FNAF animatronics, seeing the colorful and different MyStreet world, either want to destroy it or be a part of it in a very menacing way.
One plot idea could be that the characters from MyStreet end up in the FNAF pizzeria. They initially think it's just a strange place but soon realize the danger of the animatronics. Another idea is that the FNAF animatronics somehow enter the MyStreet world and start causing chaos among the peaceful MyStreet community. For example, Freddy might try to take over the local diner in MyStreet, thinking it's his territory.
A possible plot could involve a character from MyStreet who is a big fan of FNAF. They build their own animatronics as a hobby, but something goes wrong and the animatronics start to exhibit the same menacing behavior as in FNAF. Or perhaps there's a crossover where the FNAF spirits possess some of the MyStreet characters, leading to a battle between the possessed and the non - possessed to save the MyStreet world.
One idea could be that the characters from Mystreet end up in the world of BatIM. Maybe Aphmau and her friends are trying to find a way back home while being chased by the Ink Demon. Another could be a character from BatIM somehow enters the Mystreet universe and causes chaos among the residents there.
Another interesting concept is a crossover with a high - fantasy world like The Lord of the Rings. The Mystreet characters could be transported to Middle - earth. They would have to deal with orcs, wizards, and all the magic and danger that comes with that world. It would be fascinating to see how their relationships and personalities develop in such a different and dangerous environment.
One idea could be that Foxy from FNAF crosses over into another universe where he teams up with a group of unlikely heroes. Maybe he uses his speed and stealth to help them in a battle against a common enemy.
A possible plot could involve the souls in Undertale having some connection to the spirits that are rumored to be in the FNAF animatronics. The main character from Undertale, perhaps Frisk, could enter the FNAF world and try to free the trapped souls. In return, the animatronics could help Frisk in the Undertale world against some powerful foes.
Well, it could be that there is a glitch in the multiverse that causes a fusion of the two worlds. So we have characters like Frisk interacting with Freddy Fazbear. Frisk might try to show the animatronics a different way of living, more like the pacifist way in Undertale. And in the process, they all have to deal with the threats that exist in both worlds, like the purple guy from FNAF and the more malevolent monsters from Undertale.
One idea could be a time - travel plot. Maybe Aphmau gets sent back in time to the early days of Mystreet and has to navigate the relationships and events all over again, but this time with her future knowledge. This could lead to some really interesting changes in her relationship with Aaron.
Aphmau from MyStreet and Freddy Fazbear would be an interesting combination. Aphmau is a strong - willed leader in her world, and seeing her face off against Freddy, the iconic animatronic from FNAF, would be exciting. Another interesting pair could be Aaron from MyStreet and Foxy. Aaron is often protective, and Foxy has that unpredictable nature.
One idea could be that the characters from Gravity Falls end up in the FNAF world. Dipper might be intrigued by the mystery of the haunted animatronics and try to solve it using his journal. Mabel could befriend the more friendly - looking animatronics, like Chica, and try to make them cute accessories. Another plot could involve the FNAF villains getting loose in Gravity Falls and the Pines family having to use the town's unique magic to stop them.
One idea could be that the characters from Sister Location end up in an alternate universe where they have to team up with the original FNAF characters to fight a new, more powerful animatronic threat. This would bring a lot of interesting character dynamics as they try to figure out each other's motives and abilities.
One idea could be that Sonic and his friends accidentally end up in the FNAF universe. Sonic's speed could be a huge advantage against the animatronics. For example, he could quickly dash around the haunted pizzeria, confusing the animatronics and leading them into traps. Another idea is that the animatronics from FNAF somehow get transported to Sonic's world. The chaos that would ensue as they try to adapt to the bright, colorful and fast - paced Sonic world would be really interesting to write about. Maybe Sonic and Tails would have to figure out a way to send them back while also protecting their friends from the animatronics' unpredictable behavior.