Nose

A nose is a part of the animal anatomy. The nose is essential to breathing and the sense of smell.

When Marvin and Wendy were in a dark room in the Electric Generator Plant, Wendy searches for a light switch, so as to turn on the lights, but instead of finding a light switch, she found Marvin's nose.

When Wonder Dog is about to sneeze in the Nal Library, Marvin covers his nose with his finger.