pamplemousse looks down on tuna, both figuratively and literally. it's in her nature to be controlling, and it's in tuna's nature to be easily influenced (but not without retaliation), so moumou beleives she has found herself the perfect minion.

tuna is younger than pamplemousse, so he looks up to her as an older sister. still, because of his free-spirited personality, he hates when moose bossess him around. he likes to retaliate by taking advantage of how gullible she is, playing pranks on her whenever he gets the chance.