Mine one is New Super Mario Galaxy X.
I played it, together with Restoration, Mario Classic and Star Expedition before I got into Youtube video making.
At that time, I was very bad at the game like I didn't change my key binds and couldn't finish the episode in 6 videos.
Now I think about it, the quality of those videos are very bad, very laggy and just bland gameplay, compared with my current blue background, minimized lag and video editing skills.
The episode was decent, Bowser/Bowser Jr/Final level were brutally hard ( Especially the second Bowser Jr level where the creator interrupts the episode, it have no checkpoint ). I still think that it is good, that I made a boss rush video about it.