Okay, but seriously, why does everyone call Bill an isosceles monster??? That is such an inaccurate name for him!
I mean, he's obviously an EQUILATERAL monster instead. He's got three equal sides, and each of his angles is 60 degrees. And if you don't believe me, the Axolotl in the time and space between time and space had said, in the Dipper and Mabel Choose-venture thing, that Bill was "60 degrees that comes in threes." That confirms that he has 3 equal angels and 3 equal sides, making him an equilateral triangle. If he truly were an isosceles, then he'd be a lot taller and much more narrow.
I'm sorry, but I've needed to get this off my chest for like, six months. Maybe more.
Come to think of it, maybe this sort of stuff is why I'm not friends with any of the "cool" people at school.