Who Am I?

Here is another little quiz I thought I'd post:-

1. I was created by Harvey Ball. I have become an icon in chat language. Who, or rather what am I?
2. My real name is Robert Zimmerman. I am an extremely famous singer. I share my name with 'a builder'. Who Am I?
3. I had a rat named Ben, and a chimpanzee named Bubbles. Who Am I?
4. I have a pet cheetah named Lightning. Who Am I?
5. I am a hard of hearing professor, who shares his name with a certain kind of maths. Who Am I?

Answers: Smiley :) , Bob Dylan, Michael Jackson, Usain Bolt, Cuthbert Calculus in Tintin comics