Part 21Donald Mustard, in the Staff Room, with the ninja.
[ Hosted / Viddler / Blip / YouTube ]
Chapter 4-D houses the staff room. Unfortunately, chapter four has a love of panels and the pressing of said panels, and so you have to discover another three.
Panel one is in the room with four giant cylinders of light, the blue ones. It's situated on the high ledge in the northeast section and is of course covered by a conduit. Afterward is the room with two Seeker Elites, and beyond that is a weapon storage room, which has the second panel above the door to the right. You have to charge jump up in between the rafters. The third is after the Star Wars lasers and before the cutscene where the ship starts to explode, underneath the walkway and positioned behind one of the pillars. You then have to backtrack to the previous section where a door's opened.
Now, the staff room easter egg is actually an easter egg inside another easter egg. The series of panels beneath the staff's pictures have to be activated in a sequence if you want to see the other hidden thing (and you have to restart the whole section if you screw it up). Here's the order: [ 6 ]
This makes the pedestal in the middle of the room rise to reveal a spinning ninja with a guitar and another picture of dear ol' Donald.
Here's the song that plays in the Staff Room, for those who actually liked it. [ MegaUpload / MediaFire ]