I finally wrote up and posted this parody of the Letterman sketches on the old Children's Television Workshop (now Sesame Workshop) TV show The Electric Company. If I can find Letterman graphics on the Web, I'll add some as appropriate.
Narrator: The newsgroups are calm, and no fires have started this morning, so the IT group has been playing Quake for the past hour.
Admins: Auuugh, right in the back! Haha, got you! You suck! I rule!
Junior admin: He's going to feel this one right through the network!
Narrator: Oh, no! The Spellbinder has walked by an open window!
Spellbinder: There'll be no fragging here.
Narrator: The Spellbinder pulls out his magic wand, and changes the "e" in network to an "o", making it a notwork! The game will be ruined!
[The admins, almost as one, stand up in their cubicles. The junior admin sits and stares in disbelief.]
Admins: What happened to the network? Who rebooted the switch?
Junior admin: Argh, right when I had him in my sights!
[The admins, except for the junior admin, start heading for the network closet, checking network and power cables as they go. The IT manager remains at his desk, dreading the barrage of calls about the network outage from the rest of the company. The junior admin stays at his desk, waiting for the admins to call out tests.]
Narrator: But wait! From out of the telephone closet,
Faster than a rolling "o"
More powerful than silent "e"
Able to leap capital "T" in a single bound
It's a word, it's a plan, it's Letterman!
Letterman: I'm Letterman.
Spellbinder: Curses! Just when it was getting interesting.
[The admins, except the junior admin, are clustered in the network closet, oblivious to Letterman.]
Admins: No, the network connections are still in place. Let me get a terminal on that switch! Yes, it's plugged into the wall.
Junior admin: Letterman, can you fix the network?
Narrator: Letterman takes the "e" from his varsity sweater, and replaces the "o" in "notwork", making it a network again! The game is saved!
Junior admin: Thanks, Letterman!
Letterman: My pleasure. Enjoy your game!
[The junior admin sits down, fires once. From the IT manager's window cube comes a loud explosion.]
IT Manager: Eit!
Admins: Who fixed it?
Narrator: Tune in next time, when our villain goes on vacation to Silicon Valley!