Flabsweat was the proprietor of a pet shop in Undertown. He often sold creatures that should not be kept as pets, such as caterbirds, banderbears, and even beings such as waifs and oakelves.

Flabsweat once caught Twig releasing the Caterbird out of its cage, but Twig later made it up to him by giving him a gauntlet covered in phraxdust. Flabsweat was so grateful for this gift that he promised to charge Twig nothing for his wares from that point on. Keeping his word, Flabsweat later allowed Twig to take Goom, Spooler, and Woodfish free of charge.