This is a very simple program I created to prank my friends. The program looks and acts similarly to the home screen, but it will display whatever you want as an answer. For example, I put this on my friend's calculator so that when he is not looking I can turn it on. When he goes back to use his calculator it looks the same but it always answers with the number 4. It is really funny to see him get so confused for a second.
Here is the TI-84 Plus version:
ClrHome
While 1
Input "",X
Disp 4
End
For the CE, you can add a line of dots to replicate the dotted line between each entry, although it doesn't look perfect.
Feel free to change the answer that the program displays. I personally like doing a random number, so that they don't catch on as quickly. I hope you like this silly program I made!