Add Defaults insults to /etc/sudoers (via sudo visudo):

$ sudo ls
[sudo] password for zntfdr:
Are you on drugs?
[sudo] password for zntfdr:
Where did you learn to type?
[sudo] password for zntfdr:
sudo: 3 incorrect password attempts

That's funny.

Sources:

• [1] https://wiki.wlug.org.nz/FunnyApplicationErrorMessages
• [2] https://github.com/sudo-project/sudo/blob/3d7755dfac61b19a4365b829a362bfca51dcad4c/plugins/sudoers/ins_classic.h
• [3] https://askubuntu.com/questions/837558/where-are-sudos-insults-stored