Alec Guinness and Grace Kelly both starred in the 1956 film, called the Swan.
During the filming Alec was given a tomahawk and he persuaded a porter to slip into Grace Kelly's bed.
She never mentioned it yet several years later in hotel in London, Alec returned to his bed after a performing in a theatre show and there was the tomahawk in his bed.
A few more years passed and one night in America, Grace Kelly found the tomahawk in her bed. 1980 after Alec was awarded an Honorary Oscar he found the tomahawk in his bed. More time passed and one day Grace Kelly was in England and opened her suitcase and there it was the tomahawk.
Sadly she passed soon after but what I love about this story is the gag lasted 26 years and was never spoken about yet handled with mystery and humour.
Sometimes we take ourselves too seriously and a little humour goes a long way as long as it's fun for both.
Laughter in the workplace keeps the energy alive. What's the best practical joke appreciated by both parties you have heard