"Vegetarian aliens from outer space", as Jon Arbuckle describes them, are small extraterrestrial beings who invade Earth to take its groceries. Jon is terrified by this, but his cat Garfield, who's not really fond of vegetables, actually enjoys the invasion.
The vegetarian aliens are green-colored bipeds with long feet and a very large single eye. Their clothing apparently consists of pants, gloves and collar, but no shirt.
An interesting detail is that they appear to have a belly button, possibly meaning that they are viviparous and have a reproductive system similar to that of Earth's placental mammals.