| Uranus is the only planet that rotates on its side. |
| The only river that flows both north and south of the equator is the Congo. It crosses the equator twice. |
| The Joshua tree is the only tree that grows in California's Mojave Desert. |
| The only rock that floats in water is pumice. |
| The penguin is the only bird that can swim, but not fly. It is also the only bird that walks upright. |
| The only lizard that has a voice is the Gecko. |
| The hummingbird is the only bird that can fly backwards. |
| Giraffes are the only animals born with horns. Both males and females are born with bony knobs on the forehead. |
| Bats have only one baby a year. |
| Bats are the only mammal that can fly. |