嘻皮笑脸 grinning
Explanation
形容嬉皮笑脸的样子，多含贬义，表示轻浮、不认真、不严肃等含义。
Describes a grinning face, often with negative connotations, indicating frivolousness, unseriousness, and lack of seriousness.
Origin Story
话说唐朝时期，有个叫李白的诗人，他虽然才华横溢，但是为人洒脱不羁，经常嬉皮笑脸，不拘小节。有一次，他去拜访一位官员，官员正在处理公务，李白却嬉皮笑脸地闯了进去，还大声喧哗。官员被他的行为弄得十分恼火，便呵斥了他一顿。李白也不生气，依然嬉皮笑脸，反倒吟诗一首，逗得官员哈哈大笑。
It is said that during the Tang Dynasty, there was a poet named Li Bai. Although he was extremely talented, he was a free-spirited and unrestrained person who often grinned and was unconcerned about details. Once, he visited an official who was busy with official business. Li Bai, however, burst into the room with a grin, making a lot of noise. The official was very angry at his behavior and scolded him. Li Bai, however, did not get angry but remained grinning and recited a poem that made the official laugh.
Usage
常用于形容轻浮、不严肃的态度，多为贬义。
Often used to describe a frivolous and unserious attitude, mostly derogatory.
Examples
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他嘻皮笑脸地向老板解释，企图蒙混过关。
tā xī pí xiào liǎn de xiàng lǎobǎn jiěshì, qǐtú méng hùn guòguān
He explained to the boss with a grin, trying to get away with it.
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你别看他嘻皮笑脸的，其实心里很精明。
nǐ bié kàn tā xī pí xiào liǎn de, qíshí xīnlǐ hěn jīngmíng
Don't look at his grinning face, he's actually very smart.
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面试时，他嘻皮笑脸的，给人感觉很不专业。
miànshì shí, tā xī pí xiào liǎn de, gěi rén gǎnjué hěn bù zhuānyè
During the interview, his grinning seemed unprofessional.