i-adjective
Colloquial and emphatic; often used to dismiss something as utterly ridiculous or not worth taking seriously. The ちゃんちゃら part adds a mocking, childish tone.
そんな言い訳、ちゃんちゃら可笑しいよ。
That excuse is just ridiculous.
彼の話はちゃんちゃら可笑しくて、誰も信じなかった。
His story was so absurd that nobody believed it.