fine-feathered friend

all-weather friend

One who is friendly, helpful, or available at all times regardless of the circumstances.

asking for a friend

Indicates that a question is embarrassing by pretending to be posing the question on behalf of another person.

fair-weather friend

One who is friendly, helpful, or available only when it is advantageous or convenient to be so.

feathered friend

A bird.

friend of Bill W.

A recovering alcoholic, especially one who is a member of the organization Alcoholics Anonymous.

friend with benefits

A friend with whom one has a casual sexual relationship.