Scribble Mode is a visual mode typically drawn by Andrew in order to emphasize a particularly silly/stupid moment in the story, particularly those to be imagined by a character. It is similar to Hero Mode in the sense it is a style frequently used to emphasise a particular mood.
Scribble Mode is recognized thanks to its overly cartoonish and generally less artistic style, often looking close to a child's style of drawing. The style has cropped up frequently, both as a way to represent silly ideas of the kids, as well as parts of the Exiles story. Scribble Mode is often associated with ponies, THIS IS STUPID!, and the sound effect "bluh."