A similar looking although considerably less attractive person who is included in activities in order to make their counterpart look better by comparison.

Doppelganger + minger = Doppelminger.

The doppelminger is often unaware of their status as doppelminger, or sometimes uses the relationship for their own advantages (for example, becoming cool by association)

v. collectively or individually finding someone/something to blame for a problem, as opposed to brainstorming which connotes finding solutions to a problem

n. the act of finding someone/something to blame for a problem

(from a TV ad for HD television)

A person who looks like another person, except materially less good looking.