like the cat that got the cream
BRITISH or like the cat that ate the canary
AMERICANIf someone looks like the cat that got the cream, they look satisfied and happy with themselves because they have been successful or done something they are proud of. `Thanks a million,' he repeats, grinning like the cat that got the cream. Jules stands at one end, looking like the cat that ate the canary.
Collins COBUILD Idioms Dictionary, 3rd ed. © HarperCollins Publishers 2012