gai-happy
A gai-happy is someone who’s so happy they’re like a cocky kid who thinks they’re the best at everything and won’t shut up about it.
My neighbor saw a rainbow and started yelling, 'I’M THE BEST AT THIS!' for 20 minutes.
My brother got a B+ and acted like he won the lottery.
My teacher was gai-happy when I failed her test and she didn’t even notice.