Mooch is a sheepdog mix who is around the same age as the Dalmatian puppies and had lived on General Smeadley's farm before Roger and Anita Dearly moved in with their 101 Dalmatians. However, despite the fact that there are sheep on the farm, Mooch prefers to neglect his duty and just loaf around the farm looking as cool as he possibly can. Shortly after the Dearlys moved in, Mooch convinced Whizzer and Dipstick to join up with him and start their own gang; Mooch also persuaded Two-Tone to join because she considers him to be attractive, though she's also interested in the prospect of being cool. He and his gang tend to steal things from the Dearly Farm, especially food that Nanny is cooking, as they like to partake in the simple pleasures of life and they tend to live for the moment. Mooch always gets the biggest share of any prize they obtain, however, as he always takes credit for the successes of his gang, regardless of what the truth may be. Due to his actions, as well as the actions of his gang, Mooch has gained an ignoble reputation amongst the denizens of the Dearly Farm, but deep down, he has a heart of gold. Mooch also has a crush on Cadpig, and in the episode "My Fair Moochie" he falls in love with her and even dates her for a brief period of time.
Unlike many of the other dogs in the world, Mooch isn't a member of the Bark Brigade, despite the fact that all of the other members of his gang are members of the organization (although, he did show up during one session in "Un-Lucky"). Despite the fact that Mooch shows no interest in the Bark Brigade, he does have an interest in receiving affection from the Dearlys, as he often attempts to undermine the Dalmatians in order to ensure he can do something properly in order to receive their praise. While most of the Dalmatians tolerate Mooch's actions without saying a word, he has gained an archenemy in Lucky, as Lucky doesn't put up with Mooch's antics and he often directly opposes him, which causes the two to get into disputes on numerous occasions. Despite this, Mooch and Lucky are quite capable of getting along and they work together in some instances, though most of their time is spent arguing and bickering with one another over various matters. Mooch realizes that he isn't well-liked on the farm, which is the primary reason that he continues to behave in the fashion that he has, though despite what animals may think of him, Mooch and his gang are a force to be reckoned with on the Dearly Farm.