Grumpuses, also referred to as Grumps, are the dominant species in the world of Bugsnax, like humans in our world. They are bipedal, somewhat cylindrical creatures covered in fur, the color of which vary between individuals. Each Grumpus also has a unique nose shape and color, eye color, and tooth layout, among other physical differences.
Grumpuses have large mouths with large teeth, perfect for eating Bugsnax. When a Grumpus eats a Bugsnax, Snakification occurs, in which a part of their body changes into the food that said Bugsnak resembles. Their bodies, noses, limbs, hands, and feet can all transform in this manner, and in some cases, accessories such as "horns" and "hats" may even appear. This phenomenon is a property of the Bugsnax themselves, and likely not exclusive to Grumpuses.
Grumps express mostly both body language as facial expressions though the latter is somewhat limiting due to their form. They do not have eyebrows and use their eyelids as a substitute. The corners of their mouths can go up and down as expression but they do not have flexible cheeks to emote more than that - and for some the teeth are in the way. Due to their mouth size and limited facial movement, bright colours and structure they look reminiscent of Muppet puppets.
Their eyes are very high up, sticking out on top of the head and bulging out alike frogs. They do not have visible necks and their head blends into their body. The back of their head connects with their back at a point where it lines up with the mouth, being the bending spot of where the upper head tilts open. Their neck, chin and chest area have overlap to one another. Their hips are the other breaking point of the shape of the body.
Their front paws which function as hands are not shown to have thumbs and would technically not differ from their back paws that function as feet. Their legs tends to be in a bend position.
- Grumps are "little flip top trash can creatures".
- Filbo was the first Grumpus designed and used as a base for the others.
- Each Grumpus has a defining accessory which is a lasting item meant to identify a character after Snakification.
- The first names of Grumpuses are made by substituting letters from a common first name until it is barely recognizable. The surnames are made by combining a fun noun or adjective with a fun noun or verb.
Mentioned Grumpuses that do not appear in the game. They include:
- Bronica Lottablog- Triffany's grandmother, an explorer who greatly inspired Triffany, and who ventured to Snaktooth Island herself at some point. Photos of her can be seen in a scrapbook on Triffany's desk.
- Grumpbeard- A pirate who mysteriously disappeared from history. Triffany deduces that he is one of many who shipwrecked in Boiling Bay long ago.
- Beffica's ex-friend- A blue Grumpus who was a friend of Beffica in the past. They can be seen in a photo in Beffica's hut.
- Stone Grumps- An ancient group of Grumpuses who lived in the Flavor Falls/Garden Grove area. They created stone statues depicting both Bugsnax and Grumpuses, but no remains of their bodies are known.
- Desert Grumps- An ancient group of Grumpuses who lived in the Scorched Gorge/Sizzlin' Sands area. They created sandstone houses and ziggurats, as well as pottery and some sculptures. Their skeletal remains are found throughout the area.
- A post by the Young Horses Twitter account revealed the earliest model of a "Grumpus", which has a similar body shape, though with small horns and a much smaller face. It is referred to as "Folbo" by fans, as a reference to the "Woll Smoth" meme.