Billings: [...] What do you think, Peters? What are the chances that this "jewpacabra" is real?

Peters: "I'm estimating somewhere around point zero zero zero zero zero zero zero zero one percent.

Billings: (Sighs) We can't afford to take that chance. [...]

-- Trey Parker, Jewpacabra

(This is at about five minutes fifty seconds into the episode.)

Edit: Related Sequence post.