Dave and Mabel received an invitation to the Snake Valley Fancy...

Dave and Mabel received an invitation to the Snake Valley Fancy Dress Ball. They were wondering, what they could wear, when Dave remembered, that he'd slaughtered a cow a couple of weeks earlier and had hung the skin over the fence to cure. So, they decided they'd go as a cow, with Dave playing the front half and Mabel the back.
The ball was a great success and Dave and Mabel won the prize for the most original cossie. It was well after midnight, when they took their leave and, as it was a fine moonlit night, they decided to take a short cut home across the paddock. Off they went, still dressed as a cow, with Dave in front and Mabel behind. Halfway across the paddock they were startled to hear a loud snorting and a stamping of hooves.
"Christ", called out Mabel. "It's the bull. What'll we do?"
"You better brace yourself, Mabel", said Dave. "I'm gonna start chewin' grass"