1. Horrific-looking teeth.
2. Braces so hideous they're worthy of Frankenstein and other movie monsters.
3. Grills, dental head gear, braces with rubber bands, food in braces etc.
"Jaws" from the James Bond films. Flavor Flav. Ugly Betty.
"What are YOU smiling at, Frankenmouth?!"
"Well.. if it isn't Frankenmouth, the Bride of Frankenmouth and Frankenmouth Junior (a family of Frankenmouths).