Cartman briefs the boys on the specifics of the operation.
The ironically named Operation Cannot Possibly Fail was an ill-fated operation devised by Eric Cartman in the Season Eleven episode "The List".
The objective was to steal 'The List' from the list keeper Nelly at South Park Elementary, as she walked from Home Economics to Social Studies. As she moved through Hallway 3, Craig would be ready with a distraction device (a bullhorn) which would draw Nelly's attention, at which point Butters was to kick Nelly in the balls, allowing Kenny, waiting in "Corridor 3-Delta", to seize the list.
The plan worked up until the point where Butters kicked her in the balls. What the boys had failed to take into account was the fact that girls do not have balls, resulting in a failure and a very badly bruised and beaten Butters. However, valuable tactical data was gathered - primarily that girls do not have balls.
These important lessons were taken into account during the formulation of a second follow-up operation, entitled Operation Cannot Possibly Fail A Second Time.