Used to love drawing little mustaches and specs on photos in Newspapers the staffroom at one place I worked. A very highbrow institution that perhaps took itself too seriously. Occasionally a Wang or tits. Used to love hearing people's reactions. A couple of folk used to get proper upset. It was addressed in an all staff meeting once. I nearly died laughing.
My very first job was a hornets nest of awful senior management and absolute irreverent loonies.
One lad Used to sneak into people's offices and draw a massive cock on the whiteboard if he knew they had a visitor. They'd arrive and have to explain it. We'd be in the corridor sniggering.
The other great game there was defacing the awful posters acting as newsletters that were put up around the factory floor. Beaming pics of the senior management would soon find thenselves adorned with Hitler moustaches.
Mischief is a good thing. Embrace it.
A favourite prank of a mate of mine , was to very subtly alter wordy documents of people he didn’t like.
He’d wait until their desk top was open and unattended, go through the files until he found one he liked and then insert the words “ massive cock “ and “ big bollox “ within the body of the docs.
Quite often it would go unnoticed until the recipient got the doc lol