TL;DW: Mario blinks at a set interval even after level loads to prove legendary Japanese speedrunner of old, who even had a timing sequence named after him, of cheating by splicing. Even in the run that gave him his fame.
Quite interesting video showing different ways people can prove a run is spliced.
The interesting outcome of there being so many tiny inconsistencies in a game is that it takes a true expert of the game to effectively cheat. At which point, it gets even more sad when they do, since they clearly have the skill to actually compete.
Cheating of this sort is almost always about someone who is already very good at the game. But it's simply not enough. They want to be the greatest, or do the impossible. They want to be legends instead of just being really good. And usually the only way to do that is to cheat.