When you can see someone's butt crack and look directly into it.

Anatidaephobia is defined as a pervasive, irrational fear that one is being watched by a duck. The anatidaephobic individual fears that no matter where they are or what they are doing, a duck watches.

Anatidaephobia is derived from the Greek word "anatidae", meaning ducks, geese or swans and "phobos" meaning fear.

When someones pants are falling down and their ass crack is visable, they are then on or traveling down ass crack lane.