I know the idea has come up with Canada in recent memory: Turks and Caicos once petitioned to join several years back, and we were stupid to not take them. I seem to think we're more recently re-offered, and now they don't want to.
In the last year or so, Greenland has hinted it might consider leaving Denmark for Canada - Canada is closer, has similar culture and demographics with our far-north communities, and Canada would be much better economically for them. ON the plus sides for Canada, with the arctic ice melting, it could be a huge increase in natural resources... would also lay to rest a sovereignty debate on a certain island both Canada and Denmark are claiming.
Has this happened anywhere else?