So long and thx 4 all the fish

Inspired by "Her future is uncertain as a boomer plague is ruining her planet".
Curiously enough, the dolphins had long known of the impending demolition of Earth and had made many attempts to alert mankind to the danger. But most of their communications were misinterpreted as amusing attempts to punch footballs, or whistle for titbits, so they eventually gave up and left the Earth by their own means - shortly before the Vogons arrived. The last ever dolphin message was misinterpreted as a surprisingly sophisticated attempt to do a double backwards somersault through a hoop, whilst whistling the ‘Star-Spangled Banner’. But, in fact, the message was this “So long and thanks for all the fish".