Idiom 7: LIKE THE CAT THAT GOT THE CREAM
Meaning: If you look like the cat that got the cream you look very pleased with yourself because you’ve achieved something (that others haven’t).
The expression is also often used with the verbs ‘be‘, ‘act‘ and ‘behave‘.
I wonder what John was talking to the boss about. He came out of her office looking like the cat that got the cream. He had this really big smile on his face. Maybe the boss has decided to give him that promotion he wanted.
Since Jennifer started going out with Alex she has been acting like the cat that got the cream. She’s fancied him for ages.