It has two whisker-like Filter Mouths and no relatives, being hunted by all carnivore cells of the level. They normally come alone or in small groups of 2-4, but can gather into large groups, normally near Large Green Plant Flakes or other areas rich with food. Large groups of Grubbies can be very annoying or very helpful, depending on if you are a carnivore or a herbivore.
It is one of only two cells with multiple mouths, the other being Megamouth.
In color and multiplicity of eyes, but not in texture and diet, Grubby somewhat resembles the omnivorous Nosey and Bloato. However, it mostly resembles Squiggly, another herbivore that appears later. Both are green herbivores with multiple eyes. Grubby may have evolved into Squiggly.
Grubby makes a high pitched "waaaaaaaa" when hit and runs away making bubbly "pdew" sounds. However, when Grubby is prey sized, it runs away with a higher pitched version of what sound it makes as a peer sized cell. They make the same sounds as Jetster.