I just had a terrible idea. "The Three Plus Epsilon Little Pigs' Cryptosystems."
Antagonist is the Big Bad Wolf, who is trying to drive the piggies out of their homes so he can get the houses on foreclosure and flip them.
First little piggie uses a Caeser cipher, and is defeated by frequency analysis.
Second little piggie uses a Vigenere cipher, but falls to either Friedman or Kasinsky analysis.
The third little piggy devises his own cipher, but doesn't realize the need for nonlinearity and thus his cipher is broken.
The fourth little piggy realizes that it's a bad idea to reinvent the wheel when your safety is at stake, and so uses a standard cipher (AES)... in ECB mode, allowing messages to be altered, causing his downfall.
Fifth little piggie uses CBC with good IVs, but messes up on key management and uses the same key for everything.
Sixth little piggie uses good key management techniques, but has a poor root key (a password just padded to length)
Seventh little piggie uses PBKDF2, but then he tries to set up a shared secret with his banker for private communication... sending the session key over an insecure channel.
Eighth little piggie uses RSA for key exchange, but doesn't sign his messages, so his banker can't be sure they came from him and therefore can't act on them.
Ninth little piggie signs his messages properly.
As you can see, epsilon is large.