In other words...

You can pretend to be serious; you can't pretend to be witty.
-- Sacha Guitry
I think humor comes from within; you are either funny or you aren't. Just look at the tv show 'Last Comic Standing', esp when they were doing the auditions. So many of the people that came were just plain bad or they thought doing something stupid was funny.
I think most of my family has a good sense of humor. My little brother Ken can get us all laughing. Of course Ken learned this from his 3 older siblings. I have said or done something more than once that tickled Brian's funny bone that he had tears in his eyes from laughing. He makes me laugh too.
My grandfather use to write little bits that he hoped to get published. I think when he submitted one and it didn't get in a magazine, he lost hope. It was called 'How to assembly the little jiffy adironack chair'. Just the title sounds humorous.
Doctors take first place when they have to be serious, esp with delicate matters. Definitely the show 'Scrubs' tries to inject humor into a very sober topic as did M*A*S*H one of my all time favorite shows.