Frisk and Chica would also be a cool combination. Frisk is all about kindness and determination, and Chica is this animatronic with a bit of a goofy side. Frisk could try to understand Chica's motives and maybe even help her find a new purpose other than scaring people at night.
Frisk could be a very interesting character to focus on. Frisk has the power of determination, which could be used in unique ways in the FNAF setting. They could befriend some of the animatronics, using their kindness and determination. Also, since Frisk is the player - controlled character in Undertale, it would be interesting to see how they adapt to the more dangerous and unpredictable world of FNAF.
I think Freddy Fazbear and Toriel would make an interesting pairing. Freddy is this big, imposing animatronic, while Toriel is a motherly figure. Their interactions could be really cool, like Toriel trying to understand what Freddy is and Freddy being a bit confused by Toriel's kindness.
Sans is an obvious choice. His laid - back yet perceptive nature would make his interactions with the FNAF animatronics fascinating. He might be able to see through their mechanical exteriors to the tortured souls within. And his ability to teleport and use his 'Gaster Blasters' could play an interesting role when dealing with the animatronics' attacks.
Naruto would be really interesting. His never - give - up attitude would make him stand out in the spooky FNAF world. He'd probably be the one to charge headfirst into danger, whether it's facing the creepy animatronics or trying to solve the mysteries of the place. He could also try to befriend the animatronics if he thought they were being controlled against their will, just like he did with some of his enemies in the Naruto world.
Definitely Mario and Sans. Sans' laid - back attitude and his powerful abilities would contrast greatly with Mario's more heroic and straightforward nature. Their conversations would be filled with humor and misunderstandings. For example, Sans might make some jokes about Mario's mustache or his choice of overalls, while Mario would be confused by Sans' skeletal appearance and his knowledge of timelines.
Naruto and Frisk would be really interesting. Naruto is all about never giving up and has a strong sense of justice, while Frisk is determined in their own way, always choosing the path of peace and kindness in Undertale. Their combined determination could lead to some great adventures and they could learn a lot from each other's ways of dealing with challenges.
Alphys and Iron Man. Alphys is a scientist in Undertale who is a bit of a klutz but also brilliant. Iron Man is a genius inventor in Marvel. They could collaborate on some crazy technological inventions. Alphys could learn a lot from Iron Man about presenting herself more confidently, and Iron Man could be intrigued by Alphys' unique approach to science that comes from the Undertale world.
I think Leonardo and Papyrus would make an interesting pairing. Leonardo's leadership and discipline could contrast with Papyrus' more naive and enthusiastic nature. They could learn from each other, like Leonardo teaching Papyrus some ninja moves, and Papyrus showing Leonardo how to have more fun. Another great pairing could be Donatello and Alphys. They are both the 'tech - smart' characters in their respective universes. They could collaborate on some crazy inventions that combine Undertale technology and Turtle - made gadgets.
I think Monika would be really interesting. In DDLC, she has that self - awareness and a certain level of power over her world. If she were in Undertale, her attempts to understand the very different rules of that world would be fascinating. She might try to use her powers to change things, but in Undertale, the concept of determination and the power of the player is very different. So seeing her interact with characters like Flowey, who also has some unique powers and knowledge, could lead to some really intense and thought - provoking scenes.
Sans is another great choice. His laid - back but extremely powerful nature in Undertale would create a lot of interesting dynamics in a Deltarune world. He could befriend or baffle the Deltarune characters. For example, his time - related abilities would be very different from anything in Deltarune, and it would be fascinating to see how he uses them in a crossover situation, like against the Darkners.