Quote from Niles in Slow Tango in South Seattle
Niles: You never said goodbye to Miss Warner? Frasier: Well, she was sleeping so peacefully. She had an early lesson. I left a rose on her pillow. Niles: Aha Frasier: "Aha," what? Niles: "Aha" this, I have a theory. Frasier: Well, why else would you say "aha"?