The ninja-replacement scale of literature

It occurs to me you can rate other works of literature by how many characters need to be replaced by ninjas to make it better. For example, for other recent reading:

Shelley's Prometheus Unbound - Would be improved if either Asia or Panthea was a ninja -- I'm not sure which would be better. Both wouldn't work, though.

Byron's Manfred - The whole bleeping cast needs to be replaced by ninjas (except for the spirits, who'd have to be tengus). And then drop-kicked off the Jungfrau.

Keats's Endymion - Ninjas would be superfluous.

This gives them ninja-replacement scores (NRS) of 1, ∞, and 0, respectively. It also works with prose -- Lord of the Rings has an NRS of 0 (the only possible improvement is ninja!Sam, but that wrecks the last line), while Pride and Prejudice has NRS = 5 (arguably).

Care to rate any others?

ETA: Ninja-replacement in Shakespeare is being discussed here.

---L.