Klaus and Roger's relationship is a classic example of sibling rivalry. They often switch between moments of mutual dislike and fleeting camaraderie. Roger is notably spiteful towards Klaus, going out of his way to make him feel hated, as seen in moments like "Great Space Roaster" and "The One That Got Away.
Their interactions are filled with humor and hostility. In "A Piñata Named Desire," Roger’s frustration is clear when, after a comment from Klaus, he violently smashes Klaus's fishbowl without a second thought.