Can a serious-minded, all business type person, develop humor and a personality?

I have always been a “get the job done” type person. I’m very analytical. I’ve noticed that if for some reason I am in a very good mood, light-hearted or giddy, my sons want to know if I’ve been drinking. I know that’s sad, but I wonder if someone that is really serious can learn to be funny, or acquire an upbeat persona without mood altering drugs or alcohol? Or am I destined to be “all-business” for the rest of my life?