If You Underestimate Mice, You'll Die (Copyright Sense)

But if you don't take us mice seriously, you'll die (copyright sense) (ネズミを甘くみると死ぬよ(著作権的な意味で)) is a dangerous mix in many ways. This is what Nazrin, the first boss of Undefined Fantastic Object (which also serves as the mid-boss of the first and fifth level), says in response to the protagonists' mockery of her mouse status (in fact, mice carry deadly infectious diseases and have killed a tremendous number of people, albeit indirectly).

Add to this the word copyright and you get "ha ha!" (in a high-pitched voice).

やぁ！僕〇ッ〇ー！！byジョン；スミス@毎日が眠い

やぁ　みんな！byトモヨヒ夢の国のナズーリンbyうらんふ

やあ！ボク、ナズーリン・・・・ハハッ♪byメリット舞踏中ようこそ、夢と魔法の王国へ！byegoやん

On rare occasions, there are illustrations with Pikachu as part of the joke.

Touhou　Touhou Project　Undefined Fantastic Object　Yuuka Kazami　Mickey Mouse

ネズミを甘くみると死ぬよ(著作権的な意味で)