Edit the file /etc/sudoers and find the line:

Defaults        env_reset

Now add ,insults to the end of the line so that it reads like that:

Defaults        env_reset,insults

From now on, sudo will insult anyone who mistypes his password. See for yourself:

[sudo] password for foo:
Hold it up to the light --- not a brain in sight!
[sudo] password for foo:
Speak English you fool --- there are no subtitles in this scene.
[sudo] password for foo:
I think … err … I think … I think I'll go home
sudo: 3 incorrect password attempts