As part of its ongoing efforts to promote every single Pokémon out there, The Pokémon Company has shared special content dedicated to Weepinbell:
Did you know? Weepinbell has a large hook on its rear end. At night, the Pokémon hooks on to a tree branch and goes to sleep. If it moves around in its sleep, it may wake up to find itself on the ground.
Source: The Pokémon Company