I think that would be pretty awesome and funny too. Imagine a trainer who treats their Pokemon like dirt. The Pokemons to like that. One day it just turns on the trainer and decides it's time to make their relationship a bit more interesting. Or imagine a nice trainer that treats their Pokemon nicely. The Pokemon falls in love with them and they live happily ever after. Would be so sweet. And I'm sure it happens a lot in the Pokemon World too.