He amused the crowd with his spontaneous riffs during the comedy show.

riffs 是 riff 的复数形式，riff 原指爵士乐或摇滚乐中重复演奏的短小乐句，后来引申为"即兴发挥的妙语"或"俏皮话"。 在喜剧表演中，spontaneous riffs 指的是表演者根据现场情况临时发挥的有趣段子或机智应答。