A Beast.

A beast (short for Bulging-Eyed Animal Sorta Thing) is a very dumb herbivorous creature which is alarmed by most things, including other beasts. They live in herds in grasslands, desert islands and mountainous areas (despite being prone to falling off cliffs). When alarmed, a beast's eyes will grow in size, and the more alarmed they are the bigger the eyes will grow. In extreme cases the eyes may grow so much that they become black holes.

About the only thing that does not frighten a beast is eating leaves. They enjoy eating a lot. Often, a beast will eat so many leaves at once that it grows a leaf on the end of its tail. When the leaf is picked off (either by the beast it is growing on, or by another beast) it is very startling, but it does not hurt the beast. The purpose of this is unknown, but it is thought it may help young beasts to identify the types of plant that their parents eat.

It is still uncertain whether the appendages on top of a beast's head are actually ears, horns or antennae.

(Beasts are animals I doodle on nearly all the paper I come across. They look pretty much just like this - 2 ovals, stick legs, squiggle tail, dot eyes, little stick horns/ears/antennae)