My mind is blown.
I was just reading Steve Sanders very, uh, interesting Donkey Kong book from 1981 and it actually taught me something that I did not know (and believe me, for this book, that is a feat).
I haven't seen anyone else mention this either so here goes:
It turns out you can actually leech Kong on the rivets WITHOUT pressing the stick left/right! You just have to get superclose (you need to get closer on the left side than on the right). Obviously you have to be on the exact pixel, and you're screwed if you get too close, but if you're able to nail it, you can leech Kong just by pressing jump!
When I read that I just thought it was incorrect (this book has at least one inaccuracy per paragraph), but I fired up MAME just to make sure and I'll be damned.
Am I the only one who did not know this?
Actually, back in the day, that was the only way I did it. Funny thing is when my daughter was watching me play when I first got my machine, she ended up playing and she got to the rivets and I walked up on her and there she was leeching kong because she saw me doing it, she just got close enough to make it work.
The reason it works is because when you jump the program looking so many pixels left and right for an object that can kill you (say 5 pixels), when you press left or right, the range is increased to I think 19 pixels left and right, because it thinks you are running and jumping and it is neccesary to open it up that wide to complete the detection during a barrel jump. However, we've exploited this program routine to make it work for tons of more situations than was intended. (leeching kong, leeching springs as they pass, leeching fireballs as the chase you, etc..)
And if no one has ever read D2K JEFF's analysis of certain DK bugs, this reading is a treat to describe behind the scenes stuff:
http://www.jeffsromhack.com/products/donkeykong_tech.htm