Appearance:
* As flat as a pancake: This emphasizes the lack of hills or elevation.
* As smooth as a sheet of glass: This highlights the lack of texture or roughness.
* As barren as a desert: This compares the lack of vegetation or features.
* As simple as a white wall: This focuses on the lack of ornamentation or complexity.
Character:
* As straightforward as a ruler: This emphasizes honesty and directness.
* As clear as a crystal: This highlights the lack of ambiguity or deception.
* As humble as a daisy: This compares to a simple and unassuming nature.
* As basic as a pencil: This emphasizes simplicity and functionality.
Food:
* As bland as boiled potatoes: This emphasizes the lack of flavor or excitement.
* As plain as a bagel: This compares to a simple and unadorned food item.
Other:
* As dull as dishwater: This emphasizes the lack of interest or excitement.
* As boring as watching paint dry: This highlights the lack of action or stimulation.
* As straightforward as a straight line: This compares to a direct and uncomplicated path.
Remember: The best simile for "plain" will depend on the specific context and what you want to emphasize.