Oh no

The phrase "Oh no" or "Oh noes" is a recurring phrase in the Baldi's Basics series, with possible hidden lore to be uncovered in Baldi's Basics Plus.

1st Prize's quote
If the player escapes 1st Prize's line of vision, 1st Prize can say "OH - no". It is worth nothing that 1st Prize pauses mid-sentence.

Beans' quote
Once Beans spits a bubblegum, he can say "Oh no!".

The Test's body filename
The filename of The Test's body sprites is labeled as, likely because when the player approaches, he makes them blind.

Save file error
When pressing in the name with lost or corrupted save files, then the screen will appear and the first sentence of the text in the error screen is "Comic Sans MS".

Arts and Crafters charging filename
The filename for the sprite for Arts and Crafters when he charges at the player in Baldi's Basics Classic, Birthday Bash and Field Trip demo: Camping or when the player collect all notebooks and reaches the last exit in the cafeteria in Story Mode in Birthday Bash is titled as. This is reasonable as Arts and Crafters charging at the player is rarely good for them.

99 jumpscare
The audio file for the 99 game over jumpscare from Baldi's Basics Classic and Baldi's Basics Birthday Bash is labeled as.

HOW TO PLAY
In the story for Baldi's Basics Classic in the "Comic Sans MS" screen, the first sentence is "Comic Sans MS".