One of the advantages that iMessage has over text messaging is that an indicator is displayed when the other person in the conversation is typing a message. This simple animation gives you a heads-up of an incoming message; I often find myself staring at the dancing dots until the message eventually comes through.
That same feature can also be the center of a prank. Yesterday I spotted a tweet from @Panzer linking to a GIF-based iMessage prank. I wasn't sure what to expect when I clicked on the link, but I was not disappointed.
What you'll need to do in order to pull off the prank is visit this page on the Miscellaneous Mischief Web site using your iPhone. Save the GIF displayed under Step 1 to your iPhone's Camera Roll by placing your finger on the image until the prompt to save is displayed. Don't worry if the picture isn't moving when you view it in your Camera Roll, it will become animated as soon as you tap Send in iMessage.
Once you have that GIF saved to your iPhone, you can copy and paste it into any iMessage conversation and it will give the impression to the recipient that you're typing. And typing. And typing. With no end in sight.
I tested this on a few different people last night, and I found the prank to be most effective when I sent it in the middle of a conversation. Sending the GIF as the first message would often lead to the recipient receiving an alert on the iPhone's lock screen, which also includes a preview of the image.
So to get the most out of the prank, I would start a conversation and begin sending a series of message to ensure that the recipient was looking at the screen, waiting for the next message to come through. Then I would paste the GIF into the text field and send. After you send the GIF, don't start typing anything. Just sit there, watching the dots move back and forth, and laugh.
One other tip when using this prank: make sure the recipient is on an iPhone, not a Mac or iPad that's also using iMessage. The GIF doesn't appear at the right size on either device, and it's obvious that shenanigans are afoot.