If it's a crossover with a magical world, then perhaps a new character could be introduced as the main character. A young wizard who befriends Manny, Sid, and Diego. This wizard could be the one to bring the Ice Age world and the magical world together. But still, Manny, Sid, and Diego would play important supporting roles as the main characters navigate through the crossover story.
One idea could be to cross the Ice Age world with a fantasy world. Have the Ice Age characters encounter magical creatures like unicorns or dragons. Another could be a crossover with a modern - day world, where the prehistoric animals have to adapt to the strange new environment full of skyscrapers and cars.
Friendship could be a major theme. Characters from two different worlds, like Balto and Scrat from Ice Age, could form an unlikely friendship. Despite their differences in species and the worlds they come from, they find common ground and support each other.
It could be really cool. Maybe Naruto and his friends could end up in the Ice Age world. They might use their ninja skills to help the Ice Age characters. For example, Naruto could use his shadow clone jutsu to gather food for the prehistoric animals more quickly.
Well, one possibility could be that the characters from Ice Age end up in the feudal Japan setting of Inuyasha. Sid could befriend Shippo, the fox demon. They might get into all sorts of comical situations together, like trying to find food in a world full of yokai. Manny, the mammoth, could be mistaken for a strange demon by some of the more superstitious villagers. And Diego might team up with Inuyasha to fight a common enemy, perhaps a powerful ice - based demon that threatens both their worlds.
A plot could involve a powerful jutsu in the Naruto universe accidentally creating a rift that leads to the Ice Age world. The Naruto characters then have to team up with the likes of Manny and Sid. For example, Sakura could use her medical ninjutsu to heal any injured animals. And in return, the Ice Age animals could show the Naruto gang how to survive in the harsh, cold environment.
Well, it could be that Naruto somehow gets transported to the Ice Age 2 world. Maybe he uses his ninja skills to help the animals there. For example, he could use his shadow clone jutsu to gather food more quickly for the starving animals during the ice age.
A fanfic could focus on the relationship between Diego and Shira. Maybe Diego wants to show Shira a special place he found in the Ice Age wilderness. It could be a beautiful hidden valley with warm springs. Along the way, they talk about their pasts, how they became the tough sabers they are now. And at the end of the journey, their bond grows even stronger.
Well, from other movies, Woody and Buzz from 'Toy Story' would be great. Woody's leadership and Buzz's bravery would add new dynamics to the Ice Age group. Also, Simba from 'The Lion King' could be interesting. His journey to become king could intersect with the Ice Age characters' journey in some way. And of course, Shrek would bring his own brand of humor and gruffness to the mix.
One idea could be a crossover with 'The Lion King'. The Ice Age characters could end up in the Pride Lands. Sid might make friends with Timon and Pumbaa, while Manny and Diego have to deal with the lions. Another could be a crossover with 'Finding Nemo'. The Ice Age gang could somehow find themselves in the ocean, trying to help Marlin find Nemo. It would be a really wacky and fun adventure.