[R. Scott]

"Please help me find a "natural" consequence to little Johnny's offense." Meanwhile, little Johnny is pulling the cat's tail while Mom is posting for the other offense.

No problem.
Johnny pulls the cat’s tail, the cat scratches Johnny.
Johnny kicks a window the window (except Plexiglas) breaks and Johnny gets cut.
Johnny smacks the old man, the old man smacks him back.

[Modernman]

Johnny pulls the cat’s tail, the cat scratches Johnny.

We own a 20 pound Maine Coon cat. My niece grabbed its tail once. She didn't like the scratch she got, nor the rubbing alcohol that was needed to clean it afterwards. Life is very good at teaching you lessons.