I used to write silly jokes or even some insults to colleagues and bosses in my job emails, at the bottom, and then change the letter colour to white so nobody knew that was there
@fesshole Those of us who still use plaintext email know. I see more signatures that are completely busted because the user spent hours fiddling with the rich text controls and completely glossed over the fact that the underlying text still has half of the email address of the user they copied from, garbled names, or my favourite: ���������