Green towel 

A habit, action or object that would be considered inconsistent with one's personality; the one anomaly in a person's pattern of behavior.

Normally, he was an organized person, but his filthy desk was his green towel.

Green towel by TaroTart October 30, 2011

green towel 

used to clean up tooth paste and sprite. A very nice accessory to have hanging off your bed

Nathan has a green towel

green towel by Corey Washington December 14, 2006