Plain Bagel 

Someone who has no "stand out" features and who is boring as hell--just like a plain bagel--no cream cheese, no jelly, no sesame seeds, NOTHING.

Anthony: Are you inviting Janet to your birthday party?
Yvette: Yes, why?
Anthony: Ughh! Don't invite her! That bitch is such a plain bagel! She'll suck the life out of your party.

Plain Bagel by BlackieDC January 29, 2009

bathroom sign [plain bagel] 

A person always null of emotion and personality. They frequently exude boring behavior. They are not the life of the party. The real bathroom signs have no face, no expressions, no personality and you can only tell their sex by their clothing.

Bobby: Have you met Dan's girlfriend yet?
Stella: OMG, I did. She is so freaking boring. How lame?
Bobby: Absolutely, she's a total bathroom sign plain bagel. No personality, she completely blends into the walls.

bathroom sign [plain bagel] by Professor Griff January 30, 2009