The earlier post on 1:5 scale trains reminded me of an excellent MOC built years ago by Shaun Sullivan. Setting my Wayback Machine to 15 years ago, I perused Shaun’s Brickshelf Gallery to dig up his Piggyback flat car from 2002.
What isn’t clear from the photo is that the train on the flatcar is actually animated. Gearing on the underside of the flatcar allows the mini train on top to circle its own track, all while the flatcar is being pulled in a consist. Originally built before the release of Power Functions, the car uses a standard 9v motor to provide power from the track.
Video back then wasn’t what it is today, but even this short clip shows what an ingenious build this was.