Enable sudo insults

$ sudo visudo

Look for line begins with Defaults, and append insults to the end.

Defaults        env_reset,insults

Save it, and clear the sudo session (sudo -K), and try sudo with a wrong password.

Source: Enable sudo insults for some laughs

HOWTO add user to sudoers list in Debian/Ubuntu

You need to have root access to do that. So the first step to become root with the following command:

ken@debian:~$ su
Password:
debian:/home/ken# visudo

Now you can add a username to the list. For example:

ken ALL=(ALL) ALL

Save the file to complete the process.

Credit: Ubuntu Forum