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 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 Like A Dead Ringer For Somebody

 

to look a million dollars = to look or feel extremely attractive

You look a million dollars in this new outfit of yours!

To Look A Million Dollars

 

Look what the cat dragged in! = Look who has come! (insulting)

Look What The Cat Dragged In

 

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.

To Look Been Dragged Through A Hedge Backwards