ATDTDA 6 why beavers?

[Keith]

'Beavers of the brain' is a play on the phrase 'Beavers on the  
brain,' but also alludes to an episode of Pinky and the Brain  
entitled 'Beaver Barter' in which the "beavers of the Brain" assist  
him in his quest for world domination by building him dams, all of  
this made possible by the power of Pinky (cf., 'Pinkerton') to  
negotiate with said beavers for payment in bubble gum, shiny things,  
and even shoes.

See also:

http://tinyurl.com/yoo5uo