When Matt Smith started playing The Doctor, the first person he looked at to base his character on was famous scientist Albert Einstein.
Is there someone who inspires you? Maybe a celebrity, sports star or someone from history? Or perhaps it's a friend, a teacher or a member of your family?
Why do they inspire you? Is there something that they do that you admire?
This comments page is now closed but you can read a selection of comments below.
"My mum and my dad inspire me. I know it's cheesy, but it's true!"
Rory, 12, London, England
"Karen Gillan because she is amazing."
Becca, 11, Kendal, England
"Lady Gaga, she is such a wicked singer!"
James, 13, Chichester, England
"My hero is Emily Davidson because as a suffragette she fought all the way. In prison to escape force feeding, when on hunger strike, she barricaded herself in her cell. Then on the 4th of June 1913 she threw herself under the king's horse and became the first suffragette martyr on the 8th of June. She is my hero because of her bravery and determination."
Helen, 12, Hampshire, England
"Taylor Swift and Bridget Medler - they are so good and have taught me I can become an actress or singer if I put my mind to it!"
Lauren, 11, UK
"The person who I love and inspires me most is Michael Jackson and Robbie Williams!"
Hollie, 9, Surrey, England
"I really get inspired by my bro because he's a footballer."
Sam, 12, Oxford, England
"Doctor Who's Matt Smith really inspires me to dream and become a doctor."
Anna, 10, Welton, UK
"I get inspired by Newsround!"
"I have lots of family members that always give me advice and inspire me to do lots of thing. My celebrity role model is Taylor Swift and Demi Lovato because they have both gone through things and then shared their advice through songs that inspire me to be stronger."
Imaan, 11, London, England
"Taylor Swift! She's amazing (in many different ways) and she's taught lots of different people that even if you're not a 'popular' person in school you can still achieve your dreams!"
Elena, 13, Belgium
"I can say all journalists on the telly because they can meet famous people, travel around the world and they are smart too. I want to be one of them if I graduate from university."
Claudia, 14, Indonesia
"David Walliams because he was really brave to swim the Thames."
Eve, 10, Chichester, England