What makes William Shatner so funny?

For those who grew up with Star Trek, we are accustomed to seeing Captain Kirk play the hero of the Starship Enterprise...a dramatic role. But then in the mid-life stages of Shatner's career, someone discovered his comedic appeal (it may have been the Zuckerman Brothers in Police Academy). When I saw him in Airplane II - the Sequel (1982) playing the part of Commander Buck Murdock, I was hooked. "Captain Kirk? FUNNY? Who'd have thunk it?"

Some notable funny quotes:

http://www.imdb.com/character/ch0006132/...

Now when I see him throw his finger franticly at the camera in his "Priceline..NEGOTIATOR!" commercial like a football referee declaring a clipping foul, I just crack up! His character in Boston Legal is also well written and perfect for Shatner's serious, dry delivery, making him come across as a ridiculous but hilarious bufoon.

But for some reason, I just don't think I should be laughing at him...yet I do. Do you?

What's the comedic magic going on here?

When any actor is "labled" in our mind as a "serious/dramatic" actor, that is how WE expect to percieve them in everything. So when an Icon like Shatner dresses like a lawyer, or any other "serious" character, then says something totally absurd, our brain is "skewed". "Probably the Mad Cow."

He wears that suit all the time, so you think he will be serious. He also was on Star Trek, and everybody knows him. He is funny. PRICELINE NEGOTIATOR!!!

Gene Hackman was the same. He was always known as a dramatic actor, probably best known for his role of Jimmy 'Popeye' Doyle in the French Connection. When Mel Brooks offered him a chance to show his comedic side in Young Frankenstein as the blind man, Gene leapt upon it. This lead to his role as Lex Luther in the Superman movies, which he became known for by a younger audience.

Most serious actors long to display their talents outside of the limited range they've been given to perform in, whether it be in different types of roles or different media to perform in. It keeps them versatile in their craft.