Aaron Webber, Sega's community manager, went on a three-week holiday and came back to find his cubicle completely remade into the Green Hill Zone from Sonic the Hedgehog. Check out the video; the attention to detail is impressive.
The best part is the rings hanging in midair, followed by the blue Robotnik/Sonic sign that spins as you whiz by at the end of the level. The clouds, trees and ramps all show a great deal of effort too. This probably took a good portion of the workday, if not all of it.
Webber's a good sport about it, and why wouldn't he be? I want to work in Green Hill Zone, too!
Who Wants To Work In The Green Hill Zone? [IGN, thanks Lee]