many happy returns- the expression is used to wish someone happy birthday. happy medium- if you reach a happy medium you are making a compromise; reaching a conclusion or decision.
on cloud nine on top of the world
One idiom describes being in love as being "head over heels."
The best place is to go on your search engine and type in "list idioms" You can also look at this question for some examples.
Nostalogic
cry unclemonkey's uncle
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Some are, some aren't. Most domesticated animals are perfectly happy being sheltered, fed, and cared for.
Some ghosts giggle when they are being mischievious. Otherwise, it's probably happy.
cry for the moon
"Clear as mud."
Let Bygones Be Bygones
beck and call