CDA

The Child Detection Agency (or CDA for short) are a group of monsters and formerly the secondary Antagonists from the movie Monsters, Inc. They wear biohazard suits throughout the film.

Monsters, Inc.
They are a C.I.A.-like group whose main job is to search and take away and/or destroy any type of children contaminant. They come in a wide variety of forms and all wear bio-hazard suits, for fear of contamination. If any human object appears in the Monster World, they arrive to destroy it and decontaminate anyone who come in contact with such objects.

The CDA is first seen arriving at the Monsters, Inc. factory after Jerry calls the agents upon hearing Charlie's alert about a child's sock on George Sanderson's back. The agents arrive at the factory to remove the sock, which is then destroyed into smithereens, and its remains are vacuumed up. Then the agents decontaminate George by shaving his fur off, having him showered, and placing a cone on his head. Waternoose also implied that the CDA had previously been dispatched to the factory at least a month earlier, presumably for the same reason as the recent dispatch. The agents are seen again arriving at Harryhausen's after the Bartender calls the CDA about a human girl nicknamed Boo in the restaurant. They arrive at the restaurant and round-up almost every patron, including Celia Mae, for decontamination, and they envelop the restaurant in a gigantic blue force field.

The CDA deployed in full force when all of Monstropolis became aware of the incidents of Boo's invasion into the Monster World, and the Monsters, Inc. facility was thoroughly searched for evidence. Upon learning that Mike Wazowski and Sulley are the ones who have brought Boo in, Mr. Waternoose tried to have the CDA arrest Mike and Sulley so that he could take Boo and forcefully extract screams from her, but they ultimately turned on him and arrested him when they learned that Waternoose would kidnap thousands of children to satisfy his own agenda.

When Sulley discovers that laugh is more powerful than scream, the Child Detection Agency no longer exists. In place of it, comes the Comedy Detention Agency. Their job also changes to solving if a joke is funny or not. Similarly, they also were responsible for acting as ushers for the company musical play "Put that thing back where it came from or so help me."

Monsters University
Merchandise and a glimpse of an agent in the UK trailer at the 2:05 mark have confirmed the CDA will make an appearance in Monsters University. In Monsters University, Roz is also seen as part of the CDA.

Disney Parks
The CDA characters are seen in various parades. CDA agents are also seen in the rides Monsters, Inc. Laugh Floor and Monsters, Inc. Ride & Go Seek

Trivia

 * CDA Agent 001 is Roz, as revealed towards the film climax of both Monsters Inc. and Monsters University.
 * Their decontamination methods are often painful.
 * Their name (Child Detection Agency) may be a take on the CIA (Central Intelligence Agency).
 * It is unknown what they look like under their biohazard suits. Even so, they resemble various "species" of monsters, so speculations can be made.