The neighbor's cat had kittens last night and now there are four adorable little kittens.

had 是动词 have 的过去式，表示"拥有、经历"。 kittens 是 kitten 的复数形式，kitten 指"小猫、幼猫"。 had kittens 是一个固定表达，字面意思是"有了小猫"，实际指"猫产崽"这个行为。