Something fishy

Girl dolphin: Mum, dad, what's happened to Billy?
Mum dolphin: Billy? Billy who dear?
Girl dolphin: Billy, my brother, your son, Billy.
Dad dolphin: Mmmm Billy, nope. Doesn't ring a bell.
Girl dolphin: (Beginning to cry) MUM, DAD! Please, please, where's Billy?
Mum dolphin: (under her breath) Bloody told you she notice didn't i?
But no, you had to go and swap our son for a badly posed resin otter.
Dad dolphin: But look at the workmanship. Lovely bit of wet fur texture, that.