One possibility is that Deadpool is on a mission in his own universe and there's a portal malfunction which sends him to the My Little Pony realm. There, he might meet Twilight Sparkle who is intrigued by this strange new being. Deadpool could try to teach the ponies some of his combat moves in a really goofy way, while the ponies introduce him to their magic and harmony. This could lead to a story where they team up to face a common threat, like an evil force that wants to disrupt the peace in both their worlds.
It could be a more action - packed story. The soldier could be from a world at war, and when he meets the My Little Pony characters, he discovers that their world is also facing some kind of danger. He then teams up with the ponies, using his combat training and the ponies' unique magical abilities to fight off the common enemy. This could be a story about how different strengths can be combined to overcome difficulties.
One interesting storyline could be Goku accidentally landing in Equestria. He might be confused at first by the colorful ponies and their magic. But then, he could start to learn about their way of life and use his strength to help them out, like when facing some big threats that the ponies can't handle on their own.
One possible interesting story could be Nate 10 using his powers to help the ponies in Equestria solve a big mystery. Maybe he teams up with Twilight Sparkle to figure out why some magical artifacts are disappearing.
One possible plot for this fanfic is that a group of ponies accidentally stumbles upon a Star Wars spaceship. They end up on board and start exploring. The Star Wars crew is initially shocked by these strange, colorful, and small equine - like creatures. But as time goes on, they notice the ponies' strong sense of friendship and loyalty. The ponies, in turn, are fascinated by the technology on the ship. They might even help the Star Wars characters solve a problem using their unique pony abilities.
Obviously, Nate 10 would be one of the main characters. And from My Little Pony, Twilight Sparkle is very likely to be a main character as she is often at the center of many adventures in the pony world.
Some interesting ideas include having Minecraft players take on the roles of ponies. They could have pony - specific tasks like gathering magical crystals instead of ores. There could also be events in the fanfiction where the Minecraft and My Little Pony universes collide in a more significant way. For example, a portal opens up between the two worlds and characters from both sides have to work together to close it or deal with the consequences. This could lead to all sorts of interactions and story developments.
One idea could be that Godzilla accidentally stumbles into Equestria. The ponies are initially terrified but then realize Godzilla is not there to harm them. They try to communicate and find a way to send him back to his own world.
One possible plot could be that Naruto somehow gets transported to the My Little Pony world. He might initially be confused by the colorful and peaceful land, but then he could use his ninja skills to help the ponies when they face a threat, like a powerful dark magic user. He could teach the ponies some of his combat moves, and in return, learn about the magic of friendship from them.
The soldier might be a bit rough around the edges at first. He could be used to a more serious and tough environment. But the ponies, with their friendly and kind nature, would probably try to make him feel welcome. For example, Twilight Sparkle might offer to show him the library and share knowledge, while Pinkie Pie would throw a party to cheer him up.