Appeared in Nature. Online.
Two friends--Felix, a physicist, and Bruno, a plumber--keep reuniting over plumbing invoices that neither remembers occurring. Maybe, Felix proposes, it's already happened in another universe. At different places, the universe pages are "sticky" (not stated, but presumably something can happen in another universe and cause it to happen in the one you exist in).
Bruno finally arrives to fix plumbing. However, if it's already fixed in this one, what will Bruno do? Fix a different universe's plumbing? How? Or was Felix using the bathroom of a different universe and this universe returned to normal?
Felix and Bruno appeared in other story, "The Word Sweep" and in "Gödel’s Doom", albeit probably in a different universe.