I just found something quite nice.
If anyone's ever watched the Yogscast Minecraft series (shadow of Israphel), you'll have heard of Fumblemore.
Well, usually if you join an offline server using the windows run command:
"C:\Program Files (x86)\Java\jre6\bin\java" -Xms512m -Xmx1024m -cp "%APPDATA%\.minecraft\bin\*" -Djava.library.path="%APPDATA%\.minecraft\bin\natives" net.minecraft.client.Minecraf t "Character"
you get Steve with a skull cape, or just Steve.
If you type in Fumblemore, you get Fumblemore :D
"C:\Program Files (x86)\Java\jre6\bin\java" -Xms512m -Xmx1024m -cp "%APPDATA%\.minecraft\bin\*" -Djava.library.path="%APPDATA%\.minecraft\bin\natives" net.minecraft.client.Minecraf t "Fumblemore"
Just thought someone might be interested.