Rodriguez Shiftless street fixie with S&S couplers, Kuwahara tandem, Trek carbon, Dolan track
My favorite tandem videos are the old highlights from the World Track championships when they used to have tandem sprints. They stopped doing these because not that many countries entered tandems anymore (and likely because it was too bloody dangerous). You'd always see a tandem crash on the videos, and they were quite spectacular. Usually what would happen would be the tandems would be in a full sprint, like 70 kmh, then the chain would come off one of them and jam somewhere along the chainstays, and evidently they'd be using a lockring to hold the rear cog in place, so the cog would be stopped by the chain and unable to unthread, thus locking up the rear wheel. So this tandem would be fishtailing all over the wooden track with its rear wheel completely locked up, and then it would hit the turn, and the driver wouldn't be able to hold it up thru the steep banking, so the bike would finally go down, still travelling at over 40 kmh. Absolutely spectacular.
I guess this is one reason why tandem fixies on the road aren't too popular.