South Park - Cartman Joins NAMBLA is episode 405 (as per production number) or #53 (as per classic counting) of South Park. It originally aired on June 21, 2000.
In this South Park episode, as you can notice in the episode title Cartman mess around again, as he decide that he is to mature to hang out with his friends (Stan Marsh, Kyle Broflovski and Kenny McCormick), so he starts to look for older male friends in an Internet chat room. In his innocence he doesn't realize that he is actually talking to internet predators (an online predator is an adult Internet user who exploits vulnerable children or teens, usually for abusive purposes).
In this south park episode Kenny fight against the nature as his mother is trying to have another baby, Kenny does not like the idea, so he continually tries to prevent the baby's conception, all which result in misfortune at Mr. McCormick's expense.
Things are getting way out of control, transforming into a great South Park adventure.
South Park Spoiler Alert!
(The complete plot for this South Park Episode)
Cartman decides he is too mature to hang out with Stan, Kyle, and Kenny after Cartman disapproves of poor couples (like Kenny's parents) having more children, so he starts to look for older male friends in an Internet chat room. He stumbles upon the topic "Men Who Like Young Boys" and talks to some eager men whom Cartman believes want to be friends with him. In reality, they are actually Internet predators who prey on young boys.Meanwhile, Mrs. McCormick is trying to have another baby. Kenny does not like the idea, knowing that his parents will pay more attention to their baby instead of Kenny, his friends will stop hanging out with him and he'll have bad luck for the rest of his days once the baby sees the light of day as he has nightmares about it, so he continually tries to prevent the baby's conception, all which results in misfortune at Mr. McCormick's expense. First, Kenny hurls a fastball at his father's crotch during a game of catch, shattering his left testicle.
Cartman meets a pedophile who goes by the Internet handle Tony316 at Mel's Diner and ends up arrested for soliciting sex from a minor. The next day, Cartman goes to meet a "Mr. Hammerhead," who, to Cartman's surprise, turns out to be Mr. Garrison, who is also arrested. Cartman naïvely concludes that Stan and Kyle are behind his new "mature" friends getting arrested.
Despite Kenny's first effort, his mother gets pregnant anyway. Kenny adds morning-after pills to a chocolate milk/vodka cocktail and gives it to Mrs. McCormick, but she refuses to drink because of her pregnancy. Instead his father drinks it and as a result rushes to the bathroom where he repeatedly vomits and defecates. Later, Kenny convinces his family to go with him to North Park Funland to ride The John Denver Experience, a violent ride not recommended for pregnant women. Just like before, Kenny's father is the one who ends up hurt and ends up vomiting, defecating, and, now, draining his bloody nose into a garbage can. Having enough of this, Kenny chases Mrs. McCormick through the town with a plunger, hoping to plunge the fetus out of her. Upon seeing this, Mr. McCormick angrily chases after Kenny to stop him from hurting his mother and their fetus.
Cartman goes to see Dr. Mephesto about where he might find mature friends. Dr. Mephesto advises Cartman to join an organization known as NAMBLA, saying "you look about right." However, the NAMBLA that Dr. Mephesto is referring to is a fictional club for men who look like Marlon Brando in his later years (North American Marlon Brando Look-Alikes). Cartman finds the North American Man/Boy Love Association, asks to join, and is made their poster boy. The organization decides to hold a banquet in Cartman's honor and asks him to invite all the boys in town. Cartman does so, with the exception of Stan and Kyle.
Federal officials, having learned that NAMBLA is meeting in South Park, raid the venue. However, they discover that they have raided the wrong NAMBLA meeting, namely that of Dr. Mephesto's group. The FBI teams up with the Marlon Brando look-alikes and rushes to stop the other NAMBLA's banquet.
At the NAMBLA banquet, all the boys in town, including Stan and Kyle, who invited themselves, are in attendance. The boys are unaware of what is in store for them until the pedophiles take them to their hotel rooms, after which the boys run screaming into the halls. The Marlon Brando look-alikes and the federal officials arrive at the hotel, and a madcap chase with the boys, both NAMBLAs, and the feds ensues. Kenny, still chasing after his mother and now being chased by his father, joins in. Cartman decides that Butters should be the sacrificial lamb for the pedophiles to have their way with. Fortunately for Butters, he is sent into an empty room and leaves unharmed; but unfortunately for Mr. McCormick, he enters a dark room to search for Kenny, only to find the NAMBLA pedophiles, who, thinking that he is a young boy, "make love to him in the ass."
In the end, all of the North American Man/Boy Love Association members are arrested. Cartman backhandedly apologizes to his friends (including Butters) for almost getting them raped, saying that they will "blossom into maturity someday." The leader of NAMBLA says that he learned that America is "about the freedom to be whatever you want to be, be it black, gay, or a pedophile, and that pedophiles cannot choose to be attracted to boys, they're born that way." Kyle, thoroughly disgusted, retorts, "Dude. You have sex with children!" and Stan adds, "Yeah, you know, we believe in equality for everybody, and tolerance, and all that gay stuff, but dude, fuck you!"
The raped Mr. McCormick is loaded into an ambulance, which accidentally goes in reverse and runs over Kenny. Afterwards, Mrs. McCormick gives birth to an identical child they name Kenny, which she says has happened 51 times before. The French music that was played during the hallway scene is played during the closing credits.