A few years back (three phones ago) I had a phone that was quite prone to butt-dialing, and found myself accidentally calling the home phone quite a bit. I would get home and one of the kids would tell me that I had called accidentally when I was out running errands. One night, about this time of year, my partner and I were driving around town doing some Christmas shopping, and decided to play a practical joke on one of the kids. We dialed the home number and put the phone on speaker. When the kid answered, we pretended that we had butt-dialed, and staged a conversation about the different Christmas gifts we were going to get for the kids.
We pretended not to be able to hear the kid, but in fact, we could hear everything he said. He started off trying to get our attention, but finally he settled down and just listened. We would discuss different gift ideas, and he would offer commentary. Sweaters and underwear? "NO!" After a bit, he got his brother to pick up the extension. They were having a running commentary on our faux discussion. The star of the show was the room-sized chess set, with the carpet board, and blow-up pieces. This elicited comments of "Cool!"
There were two problems. First was, we never intended to get any of these things. Second, even if we had, where were we going to get such a chess set? I'd created the idea out of whole cloth.
Then I was reminded of my youth. One Christmas my parents bought my younger brother a bicycle, and my dad assembled it and slipped it into his room on Christmas morning. My brother's dog slept on his bed with him... and in the morning, when my brother got up, he was so groggy that he didn't notice the bicycle, and knocked it over at 7 AM. The sound scared the dog, who ran into the kitchen and pee'd all over the floor.
The following spring, the same brother (probably ten or eleven years old at the time) asked for a lawnmower for his birthday. My parents thought that he was joking, and got him something else. On the morning of his birthday, he woke up, fully expecting a new lawnmower to be square in the middle of his room, right where the bicycle had been at Christmas.
Wails came from my brother's room, and he walked into my parent's bedroom with tears streaming down his face, wanting to know where his lawnmower was.
Expectation is a bitch. My dad got dressed and took my brother to Sears, where they picked out a red Craftsman "Eager 1" lawnmower. Turns out my brother was a budding entrepreneur. All of our neighbor's lawns looked great.
So now, the kid was expecting a room-sized chess set. I didn't get him a room-sized chess set. I think the trauma scarred him for life.
Gosh that was fun!