Write a story together and see what happens. One if you starts the story and then sends it. Then the other one adds to the story and sends it back and you keep doing this back and forth until one of you ends the story or you get board with it and then if you want you can start another one. Here is an example:
Once there was a girl who went to a party......... Send
She had snuck out of her window because her parents said she couldn't go............ Send back
On the way to the party she saw a ........ Send
Horse running down the street.............. Send back
Get it? My high school boyfriend and I used to do this sometimes when we were bored but we wrote it on napkins because it was before we had cell phones. Lol!!!