Too much study I think.
Ok how to amaze your networker friends with this IOS Magic !
First tell them you can create a loopback or vlan interface without even entering a single command, even without touching Enter key once ! Go for a bet, it should minimum a decent lunch or few rounds in the local pub, don't go for less :)
Make them telnet the router of choice, the feature widely supported from 3550s to 6500s. Be confident (but better try before to guarantee the pints).
# sh int des
Make sure selected interface is not there ! Now Magic begins !
Tell them to go to configure mode, type "int loopback xxx" and NOT TO TOUCH enter ! At that point behave like you've changed your mind. Tell them you can do this even without that command.
Cool, now ask them to check if any additional options for this command, they will type "?", nothing just <cr>
Next tell them they don't actually need to type this command, ask them to do a CTRL-C (or delete the command using DEL key).
While they are doing this last step, you make funny magic moves, shake hands, mumble magic words... Assure them interface is just created.
Let them do another "sh int des" and enjoy the magic !