Level Locked Screen

Appearing often in beta builds, the Level Locked Screen is an anomaly which appears when a course is either incomplete or unable to load. Reports often describe it as a blank white screen with a small sprite of Mario, specifically the sprite from Super Mario Bros., and flashing text reading 'LEVEL LOCKED, PLEASE RESET THE GAME'.

Theorising
It is believed that the screen loads when a certain course is unable to load or has been locked by a developer to complete it. For example, the course Bob-omb Battlefield wasn't present in builds before E3 1996. By accessing the courses painting, the level wouldn't be able to load, thus loading the screen. It is also believed that the screen was created by the A.I, unable to remove from the game.

The screen is less likely to appear in later builds due to almost all the courses being completed.

Reportings
"Everything in this section should be taken with a grain of salt. These are all unverified claims""A while ago I found a beta 1995 cart of Super Mario 64 from a yard sale. I went to Bob-omb Battlefield first where there was a blank painting and a sign reading 'This area is incomplete. It is advised to leave this area soon due to corruption'. Ignoring it, I jumped into the painting. The game played the Bowser laugh and lead me to a screen with a Mario sprite with the words 'Level locked. Please reset the game.' flashing. I reset the game but, as the sign read, the game became too corrupted to play."

Trivia

 * The screen appears in some Super Mario 64 Beta Revival Hacks when accessing Bob-omb Battlefield, adding to the fact the screen cannot be removed from the game.