Game Over is a popular series of videos found on YouTube which feature characters from the Super Mario Brothers series. The original video was created by YouTube user cadburyking and a sequel video eventually was created by another YouTube user called Adsolution which continued the story.
Parts three and four were created by mrGlitch2000 shortly after the second episode was released and both garnered several millions hits on YouTube.
In September 2011, both parts three and four were deleted from YouTube by author, mrGlitch2000. The series is now considered missing save for a few select pieces of footage.
The story of the missing parts continued on where the second episode had left off and shown the depression that both Mario and Luigi felt due to the death of Princess Peach. Episode 3 had shown the Mario Brothers attempting to get on with their lives until a group of Zombies invade the castle. Luigi attempts to find out what's going on but is quickly attacked by a Hunter from Left 4 Dead
Episode 4 shows Mario realizing that the Castle in under attack and discovers his brother, who has been severely injured by the Zombies. He attempts to keep him alive, but Luigi dies in his brothers arms. Mario shortly climbs to the top of the tower and commits suicide, unable to escape the Zombies and the torment of losing his brother and the Princess.
YouTube user, Suescunsgaray created a brand new part for the Game Over series which was a "bad ending" for Episode 5, footage from Episodes 3 & 4 were included into the video and were shown in very small increments.
There's another good ending, more popular, made by Adsolution, titled "Game Over pt 5".
edit: part 3 and 4 were found