Muenster Monster was the name of a pet rat owned by Fin of the Men of Low Moral Fiber while they were stuck on Scabb Island due to the Largo Embargo. He had an insatiable appetite for cheese.
AcquisitionEditHe could be found in the same area as them running around on the floor of the Woodtick laundry.
UsageEditBarkeeper, he checked it himself, and fired the young cook for putting the rat in the soup.
This allowed Guybrush to apply for the job himself in order to get the up front wages.