The other night, Miles and I crossed the field that seperates my in-laws home from ours.  I noticed one of the cows was eating and told Miles to say 'hello to the cow.'

"Bull," he responded.

"Ok," I said, "say 'hello' to the bull."

"Hello," greeted Miles.

"Say it loud, like a cow," I encouraged.

"Moooooo!" yelled my son.

I'm sure I learned from that exchange than he did.