Cow: "Hmmm-hmm-hmmm ... (he looks up and reads the sign) 'I know I am a (coe).' ... That doesn't sound right."
(A farmer comes in, grumbling)
Farmer: "Mumble-mumble -- You're not a coe, you're a cow!"
Cow: (brightly) "I get it! Hmmm-hmm-hmm -- 'I (now) I am a cow!'"
Farmer: (walking around, the cow looks confused) "Grumble-grumble-grumble ... Listen -- 'I KNOW I AM A COW.'"
Cow: (smug) "You're not a cow!"