Mario is the main protagonist (outside Luigi and MarioMario54321) in MarioMario54321's and many other Bloopers and is the titular protagonist of the Mario franchise.
Personality
In MarioMario54321's earlier videos, Mario can be VERY crazy when he's mad, showing a much more destructive and murderous aptitude as a whole. Despite this, he cares about Luigi and MarioMario54321, even with his occasional rivalry streak towards the former. However, this personality more so comes from MarioMario54321 using Mario as a self-insert, as many YouTubers did from 2007-2008.
In the more recent videos, Mario is shown to be more akin to his 'canon' self, depicting clearer traits of heroism, bravery, and a lesser aptidude for going irrationally mad.
Gallery
Mario's appearance in Paper Mario (2000)
Mario's more modern appearance