Fizzgig was the small furry ball of attitude that Kira, the only remaining female gelfling, kept as a pet. He seemed to consist of a small round body with a cute little face and long tail, all of which were covered in thick poofy orange fur. At times, he seemed to show evidence of tiny paw-like feet, like when he angrily stamped them and screamed because Kira told him he couldn't accompany them to the Crystal Castle. However, when Fizzgig walked it looked more like he was just rapidly rolling around.
Fizzgig had a mouth that was almost as big as his whole body (similar in part to the way Pac Man's mouth is in proportion to his head... and how most Jim Henson creations are). When Fizzgig yells out of fear or anger his mouth opens wide and his tiny little pointed teeth and red felt tongue can appear surprisingly menacing. In fact, Jen met Kira in the midst of his quest by accidentally stumbling upon the frightened Fizzgig who responded by opening his mouth wide and barking, causing Jen to stumble backwards in alarm and fall into the marsh.
Ultimately, Fizzgig did join Kira and Jen on their quest and ended up playing a significant role in its success. At one point, the banished Skeksis causes the ceiling to fall on Jen, rendering him unconscious, and then kidnaps Kira. Fizzgig stays with Jen until he awakens and then helps him rescue Kira. Later, in a final showdown between the shard-bearing gelflings and the evil Skeksis, Fizzgig's snarling and persistent biting helps detain the Skeksis so that Jen is able to finally heal the crystal.