小猪喜欢在泥巴里滚来滚去，虽然弄得一身脏，却乐在其中。表达 “as happy as a pig in muck” 就借这一情景来比喻一个人 “高兴得不得了、乐不可支”。这个说法多用来描述因自身情况或目前的状态而感到非常高兴，而不能形容因为某件具体的事情而开心。

除了 “as happy as a pig in muck” 以外，也可以说 “like a pig in muck”，意思是一样的。

例句

Paul had started to hate his job, so he changed career path – now he's as happy as a pig in muck.

保罗开始讨厌起自己的工作，所以他改变了职业道路。现在他特别开心。

Noah loved his birthday – surrounded by his family, friends and lots of presents, he was like a pig in muck.

诺亚非常喜欢今年的生日，因为有家人和朋友陪伴，而且还收到了很多礼物。他开心得不得了。

On her day off, sat enjoying a leisurely coffee and curled up with her favourite book, Alice was as happy as a pig in muck.

休假日，爱丽丝坐在那里慵懒地喝着咖啡，蜷卧着看她最喜爱的书，开心极了。