The bad fish paradigm.

Sheldon: I promised Penny.
Leonard: Promised Penny what?
Sheldon: I wouldn't tell you the secret. (pause) Shhhhh!
Leonard: What secret? Tell me the secret.
Sheldon: Mom smokes in the car. Jesus is okay with it, but we can't tell dad.
Leonard: Not that secret, the other secret.
Sheldon: I'M BATMAN!! Shhhh!