Some info and a short description of this South Park episode on South Park Zone:
South Park - Lil' Crime Stoppers is 102nd episode of the Comedy Central series South Park. It originally aired on April 23, 2003.
Stan, Kyle, Cartman and Kenny decide to play detective; they go around the town solving minor "crimes" for a dollar. After they return a missing doll to a little girl, the police department recognizes the boys' efforts and officially names them, "junior deputies."
The boys' game of "police detectives" turns all too real when Sergeant Yates hires them to bust a drug deal.
South Park Spoiler Alert!
(The complete plot for this South Park Episode)
Our boys decide to play detective, so, they go around the town solving minor "crimes" in exchange of 1 USD.They first investigate the disappearance of a pie left sitting on the windowsill of an elderly couple's home. After examining the scene of the crime, the boys come up with a theory which is not based on any evidence at all, that the husband planned to murder his wife to have the pie for himself; however, before he could go through with the plan, the pie had already been eaten by their dog, where the boys found it. Horrified by their outrageous accusations, the couple hurriedly send them away, but not before giving them the dollar they had promised.
The boys' next case involves the recovery of a little girl's stolen doll. After suspecting Butters for no particular reason and having him produce a semen sample, they get a tip that Bill and Fosse have the doll. They manage to recover the doll from them, but several kids playing FBI assert jurisdictional privilege and take over the boys' case. The recovery gets the boys recognized by the Park County PD, and they are made Junior Detectives. However, it's not just honorary. Lieutenant Dawson, the department's head lieutenant, flat-out hires them and then assigns them to bust a meth lab, something that should be reserved for actual detectives. With the boys not knowing what a meth lab is, Stan knocks on the door of the lab and simply calls out, "Uh, police. Open up." The criminals open fire at the boys, but end up killing themselves, destroying the lab, and causing a great deal of property damage to the surrounding area.
Because of this incident, Dawson chews the boys out for "getting careless!" Meanwhile, other detectives mock the boys, and it is revealed to them that many of the cops on the force are corrupt. The boys are then sent to a strip club owned by the leader of Colorado's greatest drug cartel, who was behind the original meth lab. When they arrive, a bouncer takes them to the owner. As the cartel members notice that the boys are cops, an intense shoot-out ensues, though the boys have nothing more than make-believe guns.
The police show up to give the boys backup, but it turns out that two of them are working with Gino, and they shoot the one good cop, which survived. They then kill Gino, so that together they get all the money; one of those cops then kills the other, and then the last person he can't trust, himself. The boys are credited with cleaning up the police force and are offered positions as full detectives. The boys, however, find reality more intense than their game, and decide to play laundromat instead, returning to Cartman's basement. When Butters arrives he declares that, having tried for the entire episode, he has managed to "get off the load" and produce a sample. He managed to do this by thinking about Stan's Mom. However, they aren't playing detective anymore, so they no longer want a sample, though Cartman offers to clean his pants for him.