I had an idea !! Like Groudon is obese and that Kyurem will be, why not shipping them ? Groudon the hot obese and Kyurem the cold obese. They could love each other's obesity and try the fatten up the other ! Honestly I would love to see a friendship build between this two and the main theme is a friendly competition about "who's gonna fatten up the most the other ?" and they both love to be fattened and getting bigger ^^ There's the link of fatness, there's too the link of one is lava hot and the other ice cold but it can be too contrast with the rivalry Groudon - Kyogre who is a dislike one about being the better with the rivalry Groudon - Kyurem who would be a friendly one about making the other the bigger. And if others fat-related pokémons are added latter they could join the fun ! A bit like Lugia and her Anal Whore class :3