Discovered on the planet Mucus, when Jim was first crossing Major Mucus's slimy path, Snott the booger has ever since been a faithful Companion to him. That and the fact Jim's snotty friend took an almost immediate liking to the sandwich in his backpack at the time.
To describe Snott as a green blob with big googly eyes would perhaps be halfway there. He speaks his own strange language of slurping and burp like noises - only Jim seems to understand him.
Snott having no internal organs or skeleton can just about pull and morph himself into any form. He can bounce like a ball of rubber or stick to surfaces. Snott is not only a friend - he is very useful to have around...especially in a sticky situation.