How to change your default char.
So you want to change your char? First download a char you want. Google it for minecraft skins. Download it. Locate your minecraft.jar folder which will be for windows
%appdata% - roaming - minecraft
Mac - User-Library-Application Support - Minecraft- Bin- Minecraft.jar
Find the mob folder and delete the char.png.
Find your downloaded char and name it char.png and place it into the mob folder
Play and see your new char!
IMPORTANT:If you have texture packs installed, it will not work( only some texture packs make a new char work)