Why did Pharaoh ask for forgiveness in the singular ("Sa")? He was speaking to Moshe and Aharon!
Why did Pharaoh say "ha'Maves ha'Zeh"? He did not say so about the frogs, which entered their bodies and croaked!
Moshav Zekenim: Some explain that the Arbeh ate their faces and gouged out their eyes. This is death!