Demonstrates a clip originally
mentioned by BoredOfYou but not recorded. Found by accident after starting the game, and I haven't been able to set it up again. However, once I got Jimmy in a clipping state I was able to easily do it a second time, as shown.
Also shows walking on a thin ceiling beam and jumping to angle Jimmy while not falling off like sidestepping would do.
The other phone box's cutscene, which moves you but lets keep your height if you immediately press Esc, clips your head into the ceiling, so you can now escape the room's bounds by jumping. There's nothing to find OoB without your jetpack, Rocket Ship, or other flying equipment, though. Seems like you can fall for quite a while, though I haven't waited to see if Jimmy lands, wraps around, or is just stuck on the lowest height value but still doing a falling animation.
Use
this verification movie,
this XML, and
this CONF to play back. Unfortunately, due to apparently specific intro timing, I haven't been able to resync this to any other verification input or HDD after days of effort, despite it running laggy on 250k cycles and 48MB RAM. These tricks wouldn't be used here in an any% anyway, but could apply elsewhere if lightning strikes again for this clip.
Encode of the important part:
Also: I used the 1994 preset by accident, which seems to have affected load times as with a slow CPU even though I overrode the CPU speed with the .conf listed above. Might be a bug?