From The Simpsons:

% Some time later, the city honors Bart for his work.

For decimating our pigeon population, and making Springfield a less oppressive place to while away our worthless lives, I present you with this scented candle.
-- Mayor Quimby, "Bart, the Mother"

% Away from the speech, Skinner and Lisa talk.

Skinner: Well, I was wrong. The lizards are a godsend.
Lisa: But isn't that a bit short-sighted? What happens when we're overrun by lizards?
Skinner: No problem. We simply release wave after wave of Chinese needle snakes. They'll wipe out the lizards.
Lisa: But aren't the snakes even worse?
Skinner: Yes, but we're prepared for that. We've lined up a fabulous type of gorilla that thrives on snake meat.
Lisa: But then we're stuck with gorillas!
Skinner: No, that's the beautiful part. When wintertime rolls around, the gorillas simply freeze to death.

From real life:

El Paso County [CO] health officials will use an aggressive fish known as gambusia or mosquitofish this summer to try to control mosquito populations that can spread West Nile virus...

A professor who has closely studied the fish warns that gambusia are escape artists, able to follow floodwaters to infest other waterways. "Once they get established in a habitat, it's almost impossible to get rid of them," said Lee Kats, professor of ecology at Pepperdine University in Malibu, Calif. "Our evidence here shows once they get established in local streams, it's only a matter of time before the native amphibians begin to disappear."