I feel as if Mario is all over the place with character interactions. In games like Mario Sunshine, Galaxy 1&2, Odyssey, there's always an abundance of characters that are always interacting with each other, like FLUDD, Cappy, Rosalina and the Lumas, through dialouges and actions.
But then you get to the 2D games, 3D Land and 3D World and you see that characters barely talk to each other, and have next to no interactions.
Ironically, the spinoffs do a FAR better job with giving character interactions. Dark Moon's ending, and the Gamecube-Early Wii Mario Sports games are prime examples.