(as) happy as Larry
In very good spirits. The phrase's origin is unknown, but it may refer to Australian boxer Larry Foley. I was as happy as Larry when I found out that I'd gotten an A on my hardest exam.
happy as Larry
BRITISH, INFORMALIf you are as happy as Larry, you are very happy. I gave her a police badge to wear on her sleeve and she was as happy as Larry. Note: `Larry' may refer to the successful Australian boxer Larry Foley (1847-1917). Alternatively, `Larry' may come from `larrikin', a 19th century word for a hooligan or ruffian, used mainly in Australia.
(as) happy as the day is ˈlong/as a ˈclam/as ˈLarry
(informal) very happy: Grandpa’s as happy as a clam helping the children to fly their kites.