They're not kidding... no smiling allowed for your passport pictures.

First seen via an AP report: Smiling Frowned Upon in Visa Photographs

PITTSBURGH - Imagine being denied a passport for, of all things, your teeth. It could happen, but not because they're crooked. Under new rules for visa photographs that began this summer, the State Department doesn't want to see them at all, according to a story published in Sunday's Pittsburgh-Post Gazette.

From the State Department Glossary of Terms
Natural Expression - the subject's expression which should be neutral (non-smiling) with both eyes open, and mouth closed. A smile with closed jaw is allowed but is not preferred.