to look a gift horse in the mouth = to be ungrateful to someone who gives you something; to treat someone who gives you a gift badly; to ignore a suitable opportunity
Go and say “thank you” to your friend. You shouldn’t look a gift horse in the mouth.
to look like a dead ringer for somebody = very closely similar in appearance to someone else.
He is a dead ringer for my brother, isn’t he?
to look a million dollars = to look or feel extremely attractive
You look a million dollars in this new outfit of yours!
Look what the cat dragged in! = Look who has come! (insulting)
to look as if one’s been dragged through a hedge backwards = to look dirty and disheveled
Are you really going to the party looking like this? You look as if you’ve been dragged through a hedge backwards.