What English word has three consecutive double letters?

I am looking for a word that change both gender and number when i add the letter 'S'.

What Word am I Looking For ?

If you had a pizza with crust thickness 'a' and radius 'z', what's the volume of the pizza?

Can you identify the famous TV character from the rebus below?

Why do people go to bed?

What is both possible and impossible at the same time?

I have lakes with no water, mountains with no stone and cities with no buildings. What am I?

You can find some missing letters in the picture. By placing two particular letters in the spaces, you can form a nine lettered word beginning from one of the corners and going clockwise direction to the middle. Can you find out the letters and the word?

There is a wide field of corn. A goose finds its way into the field and starts running. Can you find out till which point the goose can run into the field?

Two boys were admitted to a school. When the headmaster asks them about their parents, they tell him that they have same parents (father and mother). On further inquiry, it turns out that they both share the same date for their birthday.

"Are you twins," ask the headmaster.
"No," replies the boys.

Is it possible?