If you can set him off on his pet subject, he will go on for hours.

如果你能引他谈起他最得意的话题，他会一口气扯上几个钟头。

youdao

In it was a great parade of universal love, that pet subject of the budding poet, which sounds as big as it is easy to talk about.

在这诗里，有对普遍之爱的巨大炫耀，它是萌芽诗人所钟情的主题，因为它十分堂皇叙述也容易。

youdao

We had to write a composition on the subject "My Pet."

我们得就“我的宠物”这个主题写一篇作文。

《柯林斯英汉双解大词典》

The zebra finch survives well in captivity. That makes it both a popular pet and a favorite subject for researchers.

VOA: standard.2010.04.05