by Theo Watson http://muonics.net/
add-on website: http://fffff.at/tourettes-machine/
Tourettes Machine is a firefox plugin that randomly adds swear words to yourform fields and text areas as you type.
There are two versions – moderate and extreme.
Moderate – adds insults every 3-5 words.
Extreme – adds insults every other damn word bitch.
Get the firefox addon here. (mac/pc/linux)