They can't, as one of the defining characteristics of a planet is having enough mass to be rounded under it's own gravity. Dwarf planets have no such restriction.
> They can't, as one of the defining characteristics of a planet is having enough mass to be rounded under it's own gravity.
The problem here is that "rounded" simply means "roughly spheroid". It's an imprecise term with no rules governing how far from a sphere the objects can deviate and still be considered planets or dwarf planets.
> Dwarf planets have no such restriction.
It is that restriction that separates dwarf planets from large asteroids.
The distinction between planet and dwarf planet has to do with whether or not the object has cleared its orbit of other debris.
Non-spherical objects can still be in hydrostatic equilibrium due to centrifugal forces being anisotropic.
https://en.wikipedia.org/wiki/Dwarf_planet#History_of_the_co...