In "Timmy 2000", most of the school kids are misdiagnosed with Attention Deficit Disorder and are prescribed Ritalin. One of side effects of Ritalin was hallucinations when taking higher doses. Eric Cartman saw, on multiple occasions, pink Christina Aguilera creatures.
As more and more kids are prescribed and begin taking Ritalin, they become less reactionary to stimuli and are seen in zombie-like trances. Parents, and other adults, soon after begin taking doses of their children's prescriptions.
Ritalin has not yet reappeared on South Park, but appears in South Park: The Stick of Truth as a junk item.
- "Timmy 2000" - Seen being administered to the children after being misdiagnosed with Attention Deficit Disorder.