Yeah! I love it.
I've seen it twice on my machine.
It actually happened just the other day in Allen's stream but Allen coined up just after Jumpman climbed the ladder but before he had a chance to die. Who knows, that could have been "the one" where demo Jumpman made it to the fourth girder!
Incidentally, if you start up MAME 0.106 and let it cycle (no input), it takes until the 35th cycle for Jumpman to make it. (Won't work on a machine - it only works on MAME because the random number generator always starts from an identical seed.)
I guess this is me admitting that one day I did indeed sit there in MAME and "F10" through the cycles until I saw it happen, and wrote down when it happened. I just find this particular thing interesting for some reason.
I wanna know what the probability is! It feels like 1 in 200 or so. The only way to be sure would be to watch about a million attract modes. Volunteers?
In a nutshell, if Jumpman stops at the short ladder when he has the hammer, he'll climb when the hammer expires. I don't think I've ever seen him climb the middle ladder, but it's possible that happens too.