I heard this description of a person the other day and really liked it. Basically you can describe someone as 开心果 kāi xīn guǒ - pistachio and it means they're a very happy, high mood person who makes other people happy.
The reason is that in Chinese, pistachio is 开心果 kāi xīn guǒ.
(in photo it's traditional Chinese 開心果)
开心 kāi xīn is to be happy / have a great time and 果 guǒ implies the nut. So quite literally works as referring to someone as a happy nut. Also interesting that 开心 kāi xīn is close to 开 kāi open/start your 心 xīn heart.
For those that heart animated gifs, can grab a bunch here:
(use the page numbers at the bottom to find which ones you like)
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