Best riddles with simple answers

When you do know me about me, them I am definitely something. You will always search for me. But when you know me, I am nothing. Who am I?

What does the orange do, when it takes a test?

People buy me to eat, but never eat me. What am I?

I can sizzle like bacon, I am made with an egg, I have plenty of backbone, but lack a good leg, I peel layers like onions, but still remain whole, I can be long, like a flagpole, yet fit in a hole. What am I?

I have a tail. I can fly. I'm covered in colorful feathers. I can whistle and I can talk. I am a...

As I was going to the mall I met a man with seven wives. Each wive held two bags, each bag held a mother cat, each mother cat had six babies, How many people were going to the mall?

While I am in air, I am not in oxygen. I am also in water, but not in hydrogen. I am necessary in all animals, but you won't find me in the zoo. Look in all brains and you'll find me there too. What am I?

What time of day, when written in a capital letters, is the same forwards, backwards and upside down?

My skin is green and slippery. I have four legs and webbed feet. I eat bugs and little fish. I can swim under water and hop on land. I am a...

What has one head, one foot and four legs?