UFO by Steve Speer is a completely mind-bending 4-minute animation from 1995. If you're on psychedelics right now and about to watch this, well, good luck. The short video tells the story of a little boy who gets abducted by a UFO from his backyard and taken on a bizarre trip through a dimension of aliens and their otherworldly machines. The originality of this animation sets it apart from anything I've ever seen before. The soundtrack is awesome, too, and makes me feel even more like I'm having some kind of fever dream. A part of what makes this animated short so trippy is its use of stereoscopic animation. The video was made with the program 3D-Studio (the DOS version). UFO was produced by Tony Asch for StrayLight Corp., animated by Steve Speer, and the soundtrack was made by Scott Lavender. The video was shown at Siggraph '95 and was paired with Virtual Research VR Helmets and motion seats.
Note: it helps if you have red-blue glasses when you watch this. Otherwise pick the 2D version on YouTube.