The story must be mirrored - i.e., beginning, then conclusion in the middle and then end with the beginning again - and must include a goldfish.
"Doctor, can you save it?"
“To be honest, it’s not the type of patient I usually treat…”
“Please, doctor, just try for us?”
“Okay, for you two.”
“I’m sorry, CPR just doesn’t seem to work on goldfish. It’s dea-”
“Our fish! Urk! My heart!”
"Doctor, can you save him?!"
Leaping onto the table, she glanced around furtively. Nobody near. She dipped a paw into the water, aiming for the annoyingly fast orange sushi.
“No, Lindy! Get away from that goldfish!”
Oops, there was ownerman. With an irritated twitch of her whiskers she leaped off the table and trotted away.
Temporary Fish Tank
Susie exuberantly toddled into the den. "Mommy, mommy, look what I got!"
“Not now, Susie, I’m writing,” replied her mother.
“But I caught fishy!”
Smiling, Susie reached into her diaper and pulled out a goldfish.
“Put him back into the tank!”
Fin in hand, Susie dejectedly waddled back out.