どうしたの？ばかばか言って？
わたしは、カバです：）

I'm a little bid confused. It’s a conversation, isn’t it? I tried to imagine its situation.

A: わたしは、ばかですか?
B: いいえ。あなたは、ばかではありません。わたしがばかです。

Is it okay?
Anyway, it’s a kind of practice. I think ばか is a very strong word and it makes someone feel stupid. I hope you don’t have an opportunity to use it. I’m afraid that I could tell you my intention. Sorry. My English is poor. Good luck with your studying! がんばって！

No, I was just practicing between two people with myself. Just a little practice. Thanks.