Alacrity

a·lac·ri·ty n.
Cheerful willingness; eagerness.
Speed or quickness; celerity.

"Robyn responded to Giles' request with alacrity."

There is also an adjective alacrituous.

"Giles was impressed by Robyn's alacritous response to his request."

Racoons and bears and penguins are all ala-critters