I’m older now than Grandma back then, many years ago. One of my more well considered purchases had been some nicely crafted fake vomit. “Whoops” After demonstrating its charms to the family members, my father suggested we try it on his mom. I had wet it in the sink, just before she came downstairs. I announced to the family I wasn’t feeling too well, some authentic retching sounds and a nice splat on the tile floor played really well. Dad started yelling at me, angrily telling me to clean up the mess. Grandma feeling sorry for me, started yelling at him for yelling at me, and went to clean it up herself. After a couple of attempts, she got the joke, laughed and completely enjoyed the prank.
Not family, but a few years ago, one of my landscaping employees had hidden a Gypsy Moth lure in his ex & future landscaping boss’ truck. Pretty funny to see 10 or 50 moths gathering around his truck wherever he parked it. Let it go on a few days, and no harm done. Victim also had a good laugh about it when we told him.