When you're on crack (a type of drug), you usually laugh and act a lot happier than you really should. Feeling crack happy is when you feel way happier about something than you really should.
A friend just gave you an M&M and you start jumping up and down like you've just won the lottery. Your friend says, "You're crack happy over that little M&M?"
by Alex Lennon October 15, 2007
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