as a dog with two tails 非常高兴；非常开心

【例句】
Give my husband an old motorbike to tinker with and he's as happy as a dog with two tails.
给我丈夫一辆旧摩托车修理，他会非常高兴的。

You couldn't have given Andrew a more welcome present than that bicycle; he was pleased as a dog with two tails.
你送给安德鲁的那辆自行车是他最欢迎的礼物，他简直高兴得没治了。