This is a classic for good reason. Although Camille Saint-Saens kept it under wraps during his lifetime because he thought such a frivolous piece would hurt his reputation as a “serious” composer, it has become one of his most famous works. He wrote it as sort of a musical joke that is full of quotes and references: “The Tortoise” is the “Can-can” from Offenbach’s “Orpheus in the Underworld” played at an appropriately tortoise-y tempo. “The Elephant” steals a bit from the Scherzo in Mendelssohn’s “Midsummer Night's Dream”, and among the “animals” included in the carnival are “Pianists” practicing their scales.
One fun thing about “classics” is that people like to have a go with their own versions. Our only recording right now is a chamber version with Yo-Yo Ma. Before that we had a version narrated by David Bowie—it accompanied us on many car rides before it was stolen from the front seat in downtown Minneapolis, with our then 2 and 4 year-olds shouting out the names of the animals as we got to each movement. (They could both match pitch perfectly with the violins in “Personages with Long Ears”—it came out pretty much a shriek, so I always had to make sure we had the car windows shut when we got to that movement.)
The colorful music, animal titles and musical references just invite poetry. Ogden Nash came out with a set of poems in 1949:
A recording with poems by Ogden Nash
There are several children's books, some with CDs, inspired by the music:
Carnival of the Animals: Poems inspired by Saint-Saens’ Music ed. by Judith Chernaik, illustrations by Satoshi Kitamura, Candlewick Press, 2006 (Book & CD)
Here's a video of "Tortoise", by Judith Chernaik, with illustrations from the book.
Carnival of the Animals: Classical Music for Kids by Camille Saint-Saens and Barrie C. Turner, illustrated by Sue Williams
Carnival of the Animals poems by Philip de Vos, illustrated by Piet Grobler, Front Street/Lemniscaat, 1998