look like the cat that ate the canary

[look like the cat that ate the canary] or [look like the cat thatswallowed the canary] {v. phr.} To seem very self-satisfied; look asif you had just had a great success.

Peter bet on the poorest horsein the race and when it won, he looked like the cat that ate thecanary.

When she won the prize, she went home looking like the catthat swallowed the canary.