A race of people identical in all respects to humans except for the fact that they lay eggs.
The Californian Sea Otter, as a species, eats about 30 different types of food found throughout its range. Each individual otter, however, will only eat 3 or 4 of these foods - those it was fed by its mother as a child. It will not eat the others even if failure to do so means it would starve. Maybe other, possibly larger and more dangerous creatures and monsters, have similar habits.
A continent is home to large, leathery flying beasts with a wingspan of over 70ft. Though shy, herbivorous and easily scared, it is possible that an enterprising person could domesticate them. They would be useless in war due to their timidity, but excellent if used for commercial air travel.
You type the command into the console. "Insufficient Guineapigs" the computer responds. Baffled, you retype the command. "Insufficient Guineapigs" the computer replies again. You decide you should start smaller, with a simpler command. "Insufficient Guineapigs"
What does cycling the spaceship's airlock have to do with a now-extinct Peruvian rodent?