NSA - The National Security Agency
Agent Clark has one voice when he first talks to Stan, but gets a different voice moments later. Agent Marx ends up with Agent Clark's first voice.
No other South Park boys speak in this episode, though Butters and Token are in the State Finals with Stan.
From this image we can see that Randy's name is Randal and that Stan is a member of the Webelos, one of the higher ranks of Cub Scouts.
Before McGee-zax arrives, you can see several visitor heads on signs. Also, the anal probe that was once in Cartman's ass is replicated as an antenna on the Channel 4 News van.
The planet encased in a cube refers to Star Trek: The Next Generation Episode 1, "Encounter at Farpoint," where "Q" instantly put his alien shining grid around the Starship Enterprise-D.