comfortable as an old shoe

(as) comfortable as an old shoe

Very familiar or comfortable, especially in an agreeably unpretentious or unrestrained manner. This car may have seen better years, but it's still comfortable as an old shoe to drive around in.
See also: comfortable, old, shoe

*comfortable as an old shoe

Cliché very comfortable; very comforting and familiar. (*Also: as ~.) My old house may seem small to you, but I think it's cozy. It's as comfortable as an old shoe.
See also: comfortable, old, shoe