Apologies if this is old news; the videos are like two years old on Youtube.
This is a series of Mario 64 gameplay videos with commentary by two Japanese guys (in Japanese). They are playing the roles of Saigo Takamori and Sakamoto Ryoma, two samurai from the Bakumatsu period. The entire time they speak in "period" language, sort of a goofy theatrical and probably not realistic version of 19th century Japanese. They make many references to their quest to defeat the shogunate, and the quest of "Mario-zamurai" (Samurai Mario) to defeat the green demon. What is this green demon?
The point of the game is relatively simple. In each world of Mario 64, there is a level in which there are eight red coins. In several worlds, there are also trees which, when climbed, will spawn a green 1UP mushroom that automatically glides after Mario until it touches him and he gets the 1UP. The idea of the game is to "unleash the green demon" and run frantically around the level, collecting all eight red coins and then star, before the mushroom catches up and slays Mario-zamurai. You never knew Mario 64 could be so terrifying…
Unfortunately, half of what makes it so funny is the commentary, which is all in Japanese. But as the YT comments attest, screams of terror transcend all linguistic boundaries...
The first part is pretty slow, so if you really want to see what these videos offer, I suggest started with Part 3 (the snow level)