[Bahbah]

I get an odd look on the first line..

I can understand that. It took me aback for a moment as well. :)

[null and void]

It's supposed to! Same principle as in a good joke - set up the thought process in one direction, then slam the punchline in from far left field.

It's the moment of cognitive dissonance that makes the joke really funny, or the point really sharp.

That's what forces the listener to think about it, rather than have it go in one ear and out the other...