With this prank when your victim writes your word of choice you can have your message of choice replace what your victim typed!
Step 1: Go to Settings.
Step 2: Go to General and Then Keyboard.
Step 3: Tap Add Shortcut.
Step 4: Type Desired Message.
Step 5: Or... Maybe Something a Bit More Evil.
You could look up something on Wikipedia and copy and paste... Ehehe