Here's the original artwork of Seth the rubber Serperior, drawn by  soul-silver-dragon.

Gender: Male.
Height: 8 ft. (head to belly), 24 ft. (head to tail)
Powers: his large body has some toon physics that allow him to squeeze into spaces that are too small for him, or put on very convincing disguises.

Personality
Seth used to be a top grunt of Team Rubber Rocket, but left the evil organization after a human he befriended was turned into a rubber Pokemon and their personality completely changed. He has since left Team Rubber Rocket and often foils any activity the evil organization is up to, skillfully performing infiltration missions and rescues of captures humans, Nick included. Seth doesn't get along well with Champ and Louie, and can send the duo flying with a strong slap of his tail. Despite his serious attitude when dealing with Rubber Rocket, he can be friendly, playful, and will frequently show some affection to those he views as his friends. He lives with Nick after having befriended him.