Fartholomew Fishflinger is a character in 'The Adventures of Puss in Boots" and the main antagonist of the episode Mouse. He was once a sorcerer who was on the verge of conquering the world until Arphetius turned him into a mouse. He ate everyone's soul in San Lorenzo so he can be a human again. Arphetius gave Puss in Boots a special potion that when Fartholomew eats Puss in Boots' soul, Fartholomew will vomit up all the souls. Arphetius kept Fartholomew busy until all the souls were vomited out of Fartholomew. He swore he will come back and eat their souls, Puss in Boots tried to catch Fartholomew until the evil mouse got away. However at the end it was revealed Dulcinea got him and ate Fartholomew without anyone knowing. He returns in the episode Yes posing as Sino, although it's not revealed until the next episode where it's revealed that his soul escaped from being eaten by Dulcenia and looked for sources of magic around the world. He was defeated again but promises that it's still not over. Later in the episode Uli reveals to be evil by summoning a monster from The Netherworld called The Bloodwolf and also reveals that he is the one who convinced Fartholomew to pose as Sino.
The mouse has mild-less resemblance a fat version of Stuart on the Stuart Little series.