Fart jokes....
Personally I thought It was pretty boring most of the way through. Firstly it's using sprites, so there isn't much to look at as being drawn, except for that short koopa piece which showed a bit of skill.
Also it was just like watching someone play mario, and then he farts, the end. I don't know if people find that funny still, but I guess we all have different tastes
Anyway, from the whole layout it was all pretty smooth and clean, but I didn't like it