Alot is wrong with this,
the animation was ok but could've been better the voice acting was pretty bad and didn't make me interested with the character I had more fun reading the comic then watching this, when a thomp falls they dont fall at a nice slow pace they are off screen in a second.
The voice acting, again was bad, thomps are rugged beings of stone. not "Hey Dave did you see that guy at starbucks yesterday.." Mario-cat sound like he was bored and couldn't understand him well. The biggest issue was the lip sync it was off in a lot of places and never really matched.
More on sound, there is a HUGE lack of background music, the mario bros castle theme should've been heard right off the bat, not dead silence for a few seconds then talking. Music is very important and should be used to the fullest in a movie, if you listen to it and hear nothing for more then a second add some music!
Your sound effects were off as well, when the hem-thomp hits the terrible squish soundeffect shoul've played before the other thomp sound played. a few split seconds yes, but attention to detail makes a good video. The scream didn't match at all, if your "voice actor" made that scream they need to not do it anymore, if not find a voice actor that know what there doing for your video. if you really want the current guy make him do more then 1 take of lines, have at least 5 different styles that way you can pick and choose.
I hope you will take these into consideration when you make a new video.