"Hey, let's make some prank calls!"
As a child did you and your friends ever dial a random number, local or long-distance, and engage the person who answered in some sort of manic dialog? It was sometimes very funny, at least to us, to prank some number. It was always done in small groups with one person as the lead and everyone laughing hysterically in the background. This was long before robo-calls made everyone hesitant to answer their phone and long before voicemail. The phone could ring for a long time if you wanted, and this could be just as annoying for the recipients of our brainless attempts at entertaining ourselves.
It would be far too generous to call these antics "Improv" as that takes practice and a high degree of concentration. Today if you Google the term you'll find their are apps and games which simulate the prank call process and plenty of sites that will give you ideas if you want to make this retro pastime happen on your own.
I doubt that with call blocking and no cost long distance that it's even possible to explain what we were doing. People today have so many better entertainment options between streaming music, TV, and movies, plus the entire Internet to surf. We were simply bored and might have been trying to kill time on a rainy weekend afternoon.
We all tried pranking the telephone operators once in our lives but we soon discovered these people were not to be trifled with. They knew who you were and how to scold you out of ever calling them again. They were mostly women who they took their jobs seriously and had no problem ringing you back until an adult answered. No amount of hanging up on them would ever deter them from making their point that this was an extremely bad idea.