Humor In The Classroom

Greetings,

I recently watched a video that discussed how humor in the classroom helps students learn and retain more.  The speaker referenced how students in war-torn countries, where the environment was more stressed, actually had a harder time learning and performing.

I have a colleague who has the kids eating out of his hand because of his funny style of teaching. He actually uses humor to manage the students' behavior, and it works.  I have personally noticed that if I am stressed or not in a good mood, it directly affects my students and the classroom environment. As one of my mentors has said "the teacher creates the weather."

My question is:  How important do you think humor is in the classroom? Also, what if a teacher is just not naturally funny--should they try to be humorous. In other words, is it a skill that can be learned? 

Finally, what techniques or methods do you use to create humor in your classrooom?