Dark Elf Drizz'l of 8-Bit Theater fame went from The Ditz who got outwitted by even Fighter of all people to a competent Deadpan Snarker with no reason or justification whatsoever, just so the author could shoehorn in humor that required the necessity of an Only Sane Man.
Unlike most examples here quite a few people prefer the later characterization of Drizz'l.
Part of this was that he seemed reasonable by comparison because he was surrounded by idiots
To be fair, he was only outwitted by Fighter because talking to Fighter had temporarily drained his intelligence. This effect was strong enough that the other light warriors were going to try to use it to defeat Chaos.
The protagonist of the webcomic The Lounge, Italy Ishida, seems to get a pretty large dose of this, cross pollinated with No Bisexuals.
Matt in Concession went from being a shy and polite virgin Christian boy who happened to be bisexual into a sex obsessed, diaper wearing, cross dressing, BDSM junkie who has sex with transvestites behind his boyfriends back and uses dark magic to fight priests who are trying to save the world.
