Bomble is the new baby nephew of the Gromble, and second grandson to Mama Gromble. Most likely from his unnamed sister as the Gromble's not mentioned having any other siblings. Bomble appears in episode Baby It's You, when he's accidentally switched with a human baby.
Once again, the Gromble has trouble keeping one of his sister's children happy and is probably exhausted tending to the new bonsty. To get some rest, the Gromble goes to Ickis, Krumm, and Oblina once again to babysit him. After he leaves, the trio express disappointment as they had wanted to go out for their afternoon.
They foolishly decide to take Bomble with them when they enter a human hospital to eat garbage. While distracted they accidentally lose Bomble and took a human baby by accident, while Bomble is given to the human baby's parents.
While there, Bomble basically eats and destroys the home. His wild anger and appetite cause them to put Bomble in a cage to prevent him from doing further damage. Eventually, the trio track down where Bomble is and with Krumm's help use his stetch as an opportunity to get Bomble out of the cage.
When the human mother goes to get ready to change her "son's" diaper, they make the switch and return back to the dump. The Gromble was happy to see his nephew had been well behaved. Though was concerned when he saw his nephew burp out a camera (which he had eaten from the human father), but the Gromble shrugged it off.
He then left with his nephew to take him home, only for Bomble to bite his arm and cling to it with his teeth while leaving. As they leave, the Gromble pleads for his nephew to let go of his arm.
Unlike the rest of his family, Bomble looks very different from his uncle and grandmother. He's purple with pinkish lips, sharp teeth, so far no nose as well, and side flaps. He also has two arms and only two legs, a contrast as it appears most of his family have two pairs of legs. One thing he may have inherited are the flaps are similar to his uncle's.
- Since he is the Gromble's nephew, he is most likely Chomble's brother.
- Bomble looks very different from his family, as he looks three of the of signature traits that three of his relatives display (eyestalks, the family nose and four legs. However, considering that he is a bonsty, it can be assumed that he'll develop these traits as he gets older.
- Its also noted that, the Gromble referred to Chomble as his "sister's son from her first marriage", meaning they could be half-siblings. And that Bomble's father may be Chomble's father.
- Ironically although both nephews are named, the Gromble has never said his sister's name.
- Although Bomble bites his uncle, the Gromble refuses to yell or be cruel to his nephew. Showing he has a soft spot for his relatives.