He is a Troll that lives in the dark sewers of New York City. He makes his first appearance in the episode "Old School Training" is featured in "Adventures in Trollsitting" and "The Halloween Bash" (all from Season 1). Stan never makes an appearance in Season 2.
Stan's entire body is covered in dark purple fur, except for his feet, hands, and face, which are bare and of a pale greenish skin color. His fur is longer on top of his head (which gives the impression that he has long hair) and even has some around his chin like a beard. Also interesting to note is his single eye in the middle of his forehead very reminiscent of the Cyclops. He also has a pointy nose, two fangs protruding out of his mouth, and constantly wears a green bow tie with a pair of brown pants with red suspenders. When trying to fit in with non-magical creatures, Stanley will cover up his upper body with a white shirt. He also has a special pair of glasses that permit him to appear as though he has two eyes instead of one.
Unlike most Trolls, Stan is very friendly and would never cause trouble on purpose. He is somewhat naive, always risking to be discovered by non-magical creatures by being his curious self. He can also be somewhat obnoxious, as experienced by Jake when Stanley loudly forced himself into the house at five in the morning in "Adventures in Trollsitting". In general, Stan acts like a child and wouldn't turn down an invitation at pretending to have a tea party with dolls.
Stanley himself doesn't really possess any magical powers, but his fur is indeed magical. Whenever it gets burned by the sun or by any other means, the hair will morph into a Hairball Monsters that will multiply several times before going on a feeding frenzy. This explains why Stanley lives in the sewers: he does so to avoid getting in contact with the sun and burning his fur.
One talent of Stan's would be his ability to fit inside a toilet regardless of its size. He also has good knowledge of the sewer network below the city.
Relation with Aunt Patchouli
As unlikely as it may sound, Stan is in a close relationship with Jake's Aunt Patchouli. They used to date back in college (at NYU in the '80s), but ended their relationship when Patchouli had to move away. In "Adventures in Trollsitting", Aunt Patchouli claims they're just old friends, but it is obvious they still have feelings for each other as seen from their reaction when they finally meet up. Stan even decided to head to Jake's home several hours early in order to be ready for his date and organized a night at the restaurant just for Patchouli.
- In "Old School Training", Stan's eye is completely red, but becomes a normal white in "Adventures in Trollsiting" and subsequent episodes.
- In "Old School Training", it is revealed that Fu Dog and Stanley are very good friends. They hadn't seen each other in a couple of hundred years.
- For some reason, Stan is the only Troll with fur in the entire series although other sewer Trolls are seen;
- Stan seems to be able to eat shoes and boogers.
- In order to remain unseen from the family, Jake and Haley stuff Stanley into different hiding spots: the guest room (or "shoe room"), the fridge, the iron board closet, the chimney, the shower, the basement, a basket, a regular closet, under a coffee table, and in Haley's room.
- Stan makes a cameo as a party guest in  (Season 1).
- Stan makes a cameo as a two-eyed Sasquatch called Stan Lakowski in the movie "Freddie Goes to Washington."
In "Old School Training"
- "Fuster? Hey, you're a sight for a sore eye!"
In "Adventures in Trollsitting"
- "Ya gotta let me in! I'm a Troll!"
- "Why do you think Trolls live under bridges and in the sewers? The sun is our poison."
- (dramatically) "Okay, I can take a hint. It's obvious that you HATE ME!" (sobs)
- (gulps a shoe put spits it out) "These shoes are stale. Got any boogers?"
- (When Jake reveals he burned Stan's fur)
- "What? I was trying to stay out of the sun for a reason! Do you know have any idea what happens when you burn Troll hair?"
- (shot of Troll hair multiplying into Hairball Monsters)
- (to Haley) "Sure, I'll have a tea party with your dollies."
- (in girly voice, playing with dolls) "This tea party ain't big enough for the both of us. BOOYAH!" (smashes dollies together)
- Old School Training (first appearance)
- Adventures in Troll Sitting
- The Halloween Bash (final appearance)