Carl has experienced the apocalypse thousands of times, although he wouldn't know Armageddon if it bit him on the ass.
Carl is the Wondrous Blunder, an accidentally immortal soul living a recycled existence. Despite messages and hints from a seemingly higher power, he has no idea that the multiverse is crumbling around him.
Something inexplicable is happening to reality itself and the whole thing has something to do with Carl's own Creator, a mysterious deity who recently took an extended leave from the office.
Yes, the Gods use cubicles. They're just empty right now.