[Seeing as how both of these jerks are over six feet tall and well-built, it probably doesn't even take the ball shifting for them to wind up toppling into each other. This is probably the default configuration they just have to work with here.
It also doesn't help that Undyne's trying to catch Sebastian too, since goddammit she is not letting some dumb human (as far as she knows) beat her for the Most Heroic effort!!]
Hey, you're the one who fell into me, punk! [She digs her elbow into his sternum a little deeper, which has absolutely no effect in squashing Sebastian into a more conveniently compact body or getting her balance back.] How about you get off of me, huh?!
iv
It also doesn't help that Undyne's trying to catch Sebastian too, since goddammit she is not letting some dumb human (as far as she knows) beat her for the Most Heroic effort!!]
Hey, you're the one who fell into me, punk! [She digs her elbow into his sternum a little deeper, which has absolutely no effect in squashing Sebastian into a more conveniently compact body or getting her balance back.] How about you get off of me, huh?!