One possible plot could be that the ponies from Equestria accidentally stumble into the wizarding world of Harry Potter. They could be initially confused by all the magic there which is different from their own. The ponies might try to help Harry and his friends with their unique pony magic, like Twilight Sparkle using her knowledge of spells in Equestria to solve some of Hogwarts' mysteries. And perhaps the Hogwarts students could learn about friendship in a new way from the ponies.
A plot could involve Voldemort somehow getting his hands on some pony magic and trying to use it for his evil deeds. Harry and his friends then team up with the ponies to stop him. The ponies' cutie marks could play an interesting role here. For example, a pony with a cutie mark related to courage could inspire Neville to be even braver in the face of danger. And the different houses at Hogwarts could interact with the different types of ponies, like the Gryffindors with the brave and adventurous ponies.
One possible plot could be that the ponies accidentally enter the wizarding world. They might be mistaken for strange magical creatures at first. Twilight Sparkle could be fascinated by the complex magic in Harry Potter's world and try to learn some spells, while Harry and his friends are intrigued by the ponies' unique magic of friendship.
One possible plot could be that Godzilla somehow gets transported to the world of My Little Pony. The ponies are initially terrified, but then they realize Godzilla is there because he's being chased by an even greater threat from his own world. So, the ponies, with their magic, decide to help Godzilla fight off this threat and in the process, they learn about each other's strengths and form an unlikely friendship.
One possible plot could be that some Pokemon accidentally end up in Equestria. The ponies are initially scared but then they realize the Pokemon are friendly. Together, they team up to stop an evil force that threatens both their worlds, like a powerful dark - type Pokemon and an evil unicorn. They use their combined powers of friendship and unique abilities to defeat the enemy.
One idea could be that the ponies somehow end up at Hogwarts. Maybe Twilight Sparkle could be mistaken for a new kind of magical creature and studied in the Care of Magical Creatures class. The ponies' unique magic could interact with the wizarding magic in unexpected ways, like their friendship magic causing some spells to be more powerful or have different effects.
Well, the plot could involve the ponies somehow getting transported to the Ice Age world. Maybe Twilight Sparkle could use her magic in a wrong way and open a portal. Then they'd meet the Ice Age characters like Manny, Sid and Diego. The ponies' colorful and positive nature could contrast with the harsh Ice Age environment. They could team up to solve a common problem, like finding a way back home for the ponies while also helping the Ice Age animals deal with a new threat.
One great idea could be having the ponies from My Little Pony visit Hogwarts. They could interact with the students and learn about magic in the wizarding world. For example, Twilight Sparkle would be really interested in the library at Hogwarts and might share some of her own magical knowledge with Hermione. Another idea is to have Harry Potter and his friends visit Equestria. They could help the ponies deal with a dark magic threat that is similar to Voldemort in their world.
Definitely Harry Potter and Twilight Sparkle. Harry is used to dealing with dark magic and saving the wizarding world, while Twilight is all about learning and magic in Equestria. They could share their knowledge of different types of magic and work together to solve problems. For example, when facing a powerful dark spell, Harry's experience with the Patronus charm could combine with Twilight's spell - casting skills to create a new form of defense.
One idea could be that the ponies discover Pokemon eggs in Equestria. They start to raise the Pokemon and learn about their powers. For example, Twilight Sparkle could study the different types of Pokemon moves using her magic knowledge.
Well, perhaps the magical creatures from the Harry Potter universe end up in the '300' setting. Dragons could be used by the Spartans to fight their enemies. The centaurs could also join the battle, lending their archery skills. And Harry could learn some combat skills from the Spartans, which he could then use back in the wizarding world to fight Voldemort's Death Eaters.
I think Luna from My Little Pony and Severus Snape would be quite interesting. Luna has her own struggles with her past and redemption, much like Snape. Their brooding natures could lead to some very deep and complex conversations, perhaps about forgiveness and second chances.