Fictional town in The Netherlands. No roads lead to Coevorden, no railways either. It does appear on maps, but no-one has ever been there or knows someone from Coevorden. It might be a code name for some secret militairy project. Everybody who claims to be from Coevorden or to have ever been there is part of the Coevorden-conspiracy (Dutch: Coevordencomplot). This conspiracy is probably linked to the Bielefeld-conspiracy.
Y: Sure, I was there only about two weeks ago.
X (to Z): Never trust Y again, he part of the Coevorden-conspiracy