一つ覚え

ひとつおぼえ

knowing only one thing (and repeating it often); saying the only thing one knows (at every opportunity); repeating the only thing one knows

noun adj-no

Example sentences

馬鹿の一つ覚（ばかのひとつおぼ）えのように、インターネット、インターネットって言（い）うなよ。

Is that all you can talk about - the Internet?