Marluxia, the flower elemental, is in Tangled, the world with the magic flower.
Young Xehanort, Xehanort’s youth and past, is in Toy Story, a world all about the magic of youth and how fleeting it is.
Vanitas, a literal monster of pure darkness, is in Monster Inc, a world where the real monsters aren’t evil.
I see what you’re doing Nomura. I see EXACTLY what you’re doing.
The last one is a little more interesting than that, actually. Vanitas’s thing is that he spawns the Unversed, creatures made from “Negative” emotions like anger, jealousy and fear.
Monsters Inc. is a movie where a big plot point is that laughter, a “positive” emotion is more valuable to the Monsters energy-wise than fear is.
…As for the first one, Tangled is also a movie about an extremely controlling and abusive caretaker keeping their foster child trapped in a tower. So they can use the magical power that child has for their own ends.
Which is basically what Marluxia does with Namine in Chain of Memories.