Can you solve these tricky questions?

These are the simple brain teasers and the answers are present within the questions.

Arnold Schwarzenegger has a long one. Michael J. Fox has a short one. But, Madonna does not use hers but Bill Clinton always uses his.

Can you tell what is it?

Answer: Their surname.

A five-letter word becomes shorter when you add two letters to it. What is that letter?
Answer: Short