To be 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.
(British & Australian) alsobe as happy as a clam (American)
to be very happy and to have no worries We married nine days after we met, and three years on we're happy as Larry.Since he's been at college he's as happy as a clam.