The weirdest film I think I've ever subjected myself to was something called 'Plastic Jesus' on Channel 4 (back in the days when they'd still actually go out of their way to look for off the beaten track programming). Imagine Dusan Makavejev making a film with literally no money for 'production' to speak of whatsoever, and just a bunch of friends, that sort of thing. It was a Yugoslavian production that was basically, from what my then-teenaged memory can recall, a series of freeform multiple-media (ie film vs video) vignettes representing political stuff and ideology that went straight over my head at the time.
Except for one moment in which someone (hairy and scruffy but I think sufficiently young and studenty enough to have probably been potentially attractive underneath it), after a completely non-engaging and interminable monologue to (video) camera, got up to reveal they were wearing nothing 'below' and so the frame was just several seconds of their hips, thighs and genitals; completely unrelated to whatever scene had been before or following. That at least was an eye-opener.
Another C4 one-off was 'Dollar Mambo', in I think Autumn 1994, which was basically a load of improv set to music in a setting that was supposed to represent a Latin American nightclub during some occupation and/or revolution or other. There wasn't any dialogue or narrative as such, just choreographed movement interspersed with stock footage. However, at some point, one of the female protagonists is 'slashed' with a flick-knife frontally by someone who I guess was meant to be some type of pimp, and proceeds to literally turn her boobs inside out - before the camera
and without any cutaways, just 'opening' them like a big book. That was a bit of a
moment and a half to this teenager whose primary motivation for watching late night C4 films at that time was the hope of seeing a bit of male bum or John Thomas lol