waterwarrior, your partner in PMD will be a Charmander nicknamed Carnivore
. As its nickname implies, Carnivore loves meat, and as such refuses to eat/use any Berries, Gummies, or Seeds. If Carnivore eats one of said items, it must forget the move it used most recently prior to eating that item (in the event of Carnivore somehow eating a Berry, Gummi, or Seed before using any moves whatsoever, choose the one it most recently learned). Above all else, Carnivore's favorite kind of meat is of the avian variety, and as such, whenever you encounter a Flying-type, you must let Carnivore solo it (the sole exception to this rule is when you're in Sky Tower, and that's because of how many Flying-types there are in that dungeon), and when fighting a boss who's Flying-type (with the exception of Rayquaza, because it's not a bird), Carnivore must
finish it off.
By the way, if you (the main character) aren't a Grass-type, part of Carnivore will be constantly tempted to kill you in your sleep and eat your corpse, due to its lust for meat, but another part of it doesn't want to kill you because it would be lonely without you, so to make things work out, Carnivore is able to stay near you in Pokemon Square, due to the fact that it's in public, but in dungeons, Carnivore's tactics must be set to "Go after foes" (which must be changed to "Go the other way" when you unlock it) and cannot be less than 3 spaces from you once you split up (don't use diagonals when counting spaces). Makuhita's Dojo does not count as a dungeon for the purposes of this restriction.
Have as much fun as you can!