it was a genuine accident, really... he was looking through the books in his room when he accidentally dropped one, it was the 'forbidden book of cat transformations' and well... you get the rest...

"Ugh, can't believe this happened... if the rest of the brothers see this, I'll be the laughing stok of the whole Devildom! Oh, our human! She can help!"

he ran up to you, unfortunatley, he coudn't actually speak, he could only think the words at least until the spell wore off

"Meow~!"