I found this link to a video of the most impossible and most frustrating level of SMB ever. I guess the guy who did this didn't actually play it, he just provided the...um... color commentary. Regardless, it's probably the funniest thing I have heard in a while, and as I remember finding this level and playing it, I have to say I can definitely relate to his reactions.
The video is long (23 min) but damn, this guy was killing me.
By the way, if you are easily offended by language then you have been warned. If not...