One of my favourites..........

Flight Simulator and other chat
https://forums.simviation.com/phpBB3/
https://forums.simviation.com/phpBB3/viewtopic.php?f=26&t=175001
Hagar wrote:The "Twin Beaver" story might be an April Fools hoax but the article doesn't make it clear that the Heinkel He 111Z "Zwilling" ("Twin") was certainly genuine.
http://worldwartwo.filminspector.com/2014/07/heinkel-he-111z-zwilling.html
As were the Wagner Twin J3 Cub, Messerschmitt Bf 109Z & of course the F-82 Twin Mustang. There was even a Twin Ercoupe specially built for air display flying & a Twin Tri-Pacer although this was a slightly different configuration without the twin fuselages --> http://1000aircraftphotos.com/Contributions/HornDavid/8788.htm
There are probably other examples that I can't think of right now.