User blog comment:SupcommMonroee/Suppy Points/@comment-1743498-20120501145259

And by the way, this was one I caught a while ago but never bothered bringing up.

Here's a quote from Operation Raising Hell:

"There was an assortment of tools inside, but what Tholker liked the most was the red crowbar. He grabbed it with his other hand, leaning against the wall of the elevator, and noticed some writing on it.

'Property of G. Freeman... huh. Oh well.'"

This is a direct reference to Gordon Freeman from the Half Life series. His weapon of choice is none other than the crowbar. So apparently, he exists Omni 01 somewhere which also must mean Chell and GLADOS exist as well.