[give] {sb} a melvin

to grab and pull a person's underwear or pants to make it get stuck between their buttocks, often as a prank

The origin of the idiom "give someone a melvin" is not well-documented, and its specific origins are unclear. It likely emerged as a playful or mischievous act among friends or peers. The name "melvin" itself is believed to have originated as a humorous name given to the prank. It is often employed during moments of camaraderie, joking around, or playful teasing.

During our school camping trip, my friends thought it would be funny to give me a melvin while I was setting up my tent.
The mischievous siblings were always finding ways to prank each other, and giving a melvin was one of their go-to tricks.
At the company picnic, the employees engaged in playful pranks, and one colleague decided to give the boss a melvin as a lighthearted joke.
As a group of friends, we had a tradition of giving each other melvins whenever someone celebrated a birthday, as a playful and silly gesture.
The boys giggled mischievously as they plotted to give their unsuspecting friend a melvin during recess, hoping to catch him off guard.