I wouldn't call myself a die-hard Portal fan in the least bit, but I got this reference instantly. A local news channel in Oklahoma (they won't be winning the Emmy this year!) was doing a fluff piece on some local ghost hunters and really the results are quite stupid. "We wrote "What is your name" on the caulk board and came back six months later and found "Mattie" underneath... we didn't write that."
Fucking six months huh? Yeah I'm sure that no one broke in and fucked around in there. The best part is the dude's explanation for "The cake is a lie" which is actually very accurate.
http://www.youtube.com/watch?v=dXVNvfPetxU#t=207