Is it just me or wasnt Cliff Clavin a pretty nice guy on Cheers during the Coach years? But when Woody replaced Coach,Cliff became a real pain in the butt know it all that just about everybody hated

I agree. You have to keep in mind though, that Cliff wasn't a regular at that time. So his character wasn't fully developed.

He needed to be a little more 'wierd' in order to take on a bigger role in the show I guess, otherwise he would have been too boring.

It's true that Cliff got more "weird" and tedious over the years, but everything that was quintaessentially Clavin-esque was already present in his character from day one, much to the writers' credit and John Ratzenberger's as well (he was the one who pitched the idea for the character, who shaped and defined Cliff from the very beginning). Even the "It's a little known fact..." line was said in the Pilot.

:)