Crane has said that it's not possible to cross all screens in a game (i.e. the underground must be used). A "pixel perfect" run is n/a since it takes slightly longer to cross a screen than a vine, croc jaws, or disappearing pit to cycle...you will lose time waiting for the next pass whenever you encounter a group of such screens (4 or more in a row, IIRC).
sorry, I wasn't clear - when I used a phrase 'pixel perfect' I meant jumping/crossing at the optimal possible moment. There are scenes when you don't have a choice but to wait. But, as discussed elsewhere on the forums you can jump into pits while they are still open if you time it right. You can run over when they are closed, and knowing they will open soon 'jump out' before they open below you. Some vines that appear already too far can still be caught. Of course, 'ideal' run would be extremely unlikely to be achieved by even most skilled player.
It's all very theoretical, I thought it's impossible (and yes, I've heard that David Crane said that) until I got the score above. Bar few log hits it shows that 106K is possible, and it's only then when I started thinking.
There is a huge amount of screens where you don't really have to stop - I memorized number of stages by repetition, and got really good time for 1/3rd of the run, but I kept losing lot of time on the later scenes because I wasn't familiar with them, or because my memory failed me.